Microscope and sample observation method

ABSTRACT

For a semiconductor device S as an inspected object, there are provided an image acquisition part  1 , an optical system  2  including an objective lens  20 , and a solid immersion lens (SIL)  3  movable between an insertion position including an optical axis from the semiconductor device S to the objective lens  20  and a standby position off the optical axis. Then observation is carried out in two control modes consisting of a first mode in which the SIL  3  is located at the standby position and in which focusing and aberration correction are carried out based on a refractive index n 0  and a thickness t 0  of a substrate of the semiconductor device S, and a second mode in which the SIL  3  is located at the insertion position and in which focusing and aberration correction are carried out based on the refractive index n 0  and thickness t 0  of the substrate, and a refractive index n 1 , a thickness d 1 , and a radius of curvature R 1  of SIL  3 . This provides a microscope and a sample observation method capable of readily performing observation of the sample necessary for an analysis of microstructure or the like of the semiconductor device.

RELATED APPLICATION

This is a Continuation-In-Part application of application Ser. No.10/880,100 filed on Jun. 30, 2004, now pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a microscope used for observing asample such as a semiconductor device at a predetermined observationplane and through the sample, and a sample observation method.

2. Related Background Art

In recent years, many of semiconductor devices are being fabricatedusing face down bonding and flip chip bonding with a device surface(active circuit surface) at the bottom side of a substrate. Ininspection of such semiconductor devices, it is sometimes difficult toexpose the device surface of the substrate without disassembling apackage, depending upon a type of the package and a mounting direction.Even in cases where a device surface of a substrate mounted not usingthe flip chip mounting can be exposed, but where semiconductor devicesare highly integrated or multilayered, it is becoming hard to observeinterconnections, devices, etc. in lower layers. Correspondingly, amethod proposed is one of observing a semiconductor device through asubstrate from the back side opposite the device surface.

The conventional known semiconductor inspection apparatus include anemission microscope (Japanese Patent Application Laid-Open No.H7-190946), an OBIRCH device (Japanese Patent Application Laid-Open No.H6-300824), a time-resolved emission microscope (Japanese PatentApplication Laid-Open No. H10-150086), and so on. In observation usingsuch microscopes, since silicon (Si) used as a material of the substrateof the semiconductor device transmits near-infrared light, theobservation is carried out using infrared light or the like. In recentyears, however, the semiconductor devices as inspected objects are beingminiaturized more and more, and it is becoming hard for the conventionalinspection apparatus using visible light or infrared light, to analyzethe microstructure, because of restrictions from the diffraction limitin the optical system.

For this reason, in a case where the microstructure of a semiconductordevice is analyzed to detect an abnormal portion in a circuit patternsuch as transistors and interconnections formed in the semiconductordevice, an abnormality-existing range is first narrowed down to someextent by an inspection apparatus using visible light or infrared light.Then the narrowed-down range is further observed by a method with anobservation apparatus such as an electron microscope with higherresolution to detect an abnormal portion in the semiconductor device.

SUMMARY OF THE INVENTION

The method of performing the observation in high resolution with theelectron microscope after the inspection with light as described abovehas a problem that the inspection of semiconductor device requires agreat deal of effort and time, for example, because of complicatedpreparation and installation of the semiconductor device as an inspectedobject.

On the other hand, a solid immersion lens (SIL) is known as a lens forenlarging an image of an observed object. The SIL is a lens ofhemispherical shape, or of hyperhemispherical shape called a Weierstrasssphere, and is normally a compact lens element about 1 mm to few mm insize. When this SIL is placed in contact with the surface of theobserved object, it can increase the numerical aperture NA andmagnification and implement observation in high spatial resolution.However, inspection with the SIL has not been put to practical use yetin the field of the inspection of semiconductor devices, in view of itshandling, observation control, and so on. This is also the case inobservation of samples except for the semiconductor devices.

The present invention has been accomplished in order to solve the aboveproblem, and an object of the invention is to provide a microscopecapable of readily carrying out observation of a sample necessary for ananalysis of microstructure of a semiconductor device and the like, and asample observation method.

In order to achieve the above object, a microscope according to thepresent invention is a microscope for observing a sample at apredetermined observation plane, comprising: (1) an optical systemcomprising an objective lens and adapted to guide an image of thesample; (2) objective lens driving means for driving the objective lensto achieve focusing and aberration correction for the sample; (3) asolid immersion lens arranged at a position including an optical axisfrom the sample to the optical system; and (4) controlling means forcontrolling the objective lens driving means, wherein (5) thecontrolling means has a solid immersion lens mode, as a control mode, inwhich the focusing and aberration correction are carried out under acorrection condition set based on a refractive index n₀ of the sampleand a thickness t₀ of the sample up to the observation plane, and arefractive index n₁, a thickness d₁, and a radius of curvature R₁ of thesolid immersion lens.

A sample observation method according to the present invention is asample observation method of observing a sample at a predeterminedobservation plane and through an optical system comprising an objectivelens, the sample observation method comprising: (a) a correction step ofplacing a solid immersion lens at an insertion position including anoptical axis from the sample to the optical system and carrying outfocusing and aberration correction under a correction condition setbased on a refractive index n₀ of the sample and a thickness t₀ of thesample up to the observation plane, and a refractive index n₁, athickness d₁, and a radius of curvature R₁ of the solid immersion lens;and (b) an enlarged image observation step (second image observationstep) of observing an enlarged image of the sample in a state aftercompletion of the focusing and aberration correction in the correctionstep.

The microscope and sample observation method described above are adaptedfor observation of a sample carried out through the sample and at apredetermined observation plane, such as inspection of a semiconductordevice carried out from the back side through the substrate, and areconfigured to perform the observation of the sample by using the controlmode (solid immersion lens mode) of carrying out the observation underthe observation condition set in view of the optical parameters of thesample and the solid immersion lens in the presence of the solidimmersion lens. This makes it feasible to suitably acquire the enlargedimage in the presence of the solid immersion lens, and thus to readilyperform the observation of the microstructure of the sample and thelike.

A specific example of the observation of the sample is an example inwhich the sample is a semiconductor device and in which thesemiconductor device is observed from its back side through a substrate.In this case, the aforementioned microscope is used as a semiconductorinspection apparatus, and implements easy accomplishment of inspectionsuch as the analysis of microstructure of the semiconductor device. Theoptical system for guiding the image of the sample may be provided withimage acquiring means for acquiring the image of the sample.

A solid immersion lens holder is preferably a solid immersion lensholder comprising: a base part to be attached to an objective lens; anda lens holding part provided with the base part, extending in adirection of an optical axis of the objective lens, and holding a solidimmersion lens at an end portion thereof, wherein the lens holding partholds the solid immersion lens so that light emerging from the solidimmersion lens to the base part side travels through a region outsidethe lens holding part and toward the base part, and wherein the basepart has a light passing portion which transmits the light emerging fromthe solid immersion lens to the base part side, toward the objectivelens.

Alternatively, a solid immersion lens holder is preferably a solidimmersion lens holder for holding a solid immersion lens to be used inobservation of an observation object placed in a recess of a sampleholder, the solid immersion lens holder being attached to an objectivelens, holding the solid immersion lens so as to avoid contact with aside wall of the recess during observation of a peripheral part of theobservation object, and transmitting light emerging from the solidimmersion lens to the objective lens side, toward the objective lens.

The present invention will be more fully understood from the detaileddescription given hereinbelow and the accompanying drawings, which aregiven by way of illustration only and are not to be considered aslimiting the present invention.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will beapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically showing a configuration of anembodiment of the semiconductor inspection apparatus.

FIG. 2 is a side sectional view showing a configuration of an objectivelens in the inspection apparatus shown in FIG. 1.

FIG. 3 is a side view showing a semiconductor device observation methodwith an SIL in the inspection apparatus shown in FIG. 1.

FIG. 4 is a flowchart showing an example of a semiconductor inspectionmethod using the inspection apparatus shown in FIG. 1.

FIG. 5 is a flowchart showing observation in a normal mode andobservation in an SIL mode in the inspection method shown in FIG. 4.

FIG. 6 is a figure including schematic diagrams showing (a) a defaultstate, (b) a normal mode, and (c) an SIL mode in the observation of thesemiconductor device.

FIG. 7 is a graph showing an example of correlation between refractiveindex of substrate, and geometric aberration.

FIG. 8 is a graph showing an example of correlation between thickness ofsubstrate, and focus movement amount.

FIG. 9 is a graph showing an example of correlation between thickness ofsubstrate and spacing between lens units in the objective lens.

FIG. 10 is a graph showing an example of correlation between depth ofmeasurement and focus movement amount.

FIG. 11 is a graph showing an example of correlation between depth ofmeasurement and spacing between lens units in the objective lens.

FIG. 12 is a graph showing another example of correlation between depthof measurement and spacing between lens units in the objective lens.

FIG. 13 is a configuration diagram showing another embodiment of thesemiconductor inspection apparatus.

FIG. 14 is a configuration diagram showing a side view of thesemiconductor inspection apparatus shown in FIG. 13.

FIG. 15 is a perspective view from above an embodiment of an SILmanipulator and objective lens.

FIG. 16 is a bottom view showing the SIL manipulator and objective lensin a state in which the SIL is located at a standby position.

FIG. 17 is a bottom view showing the SIL manipulator and objective lensin a state in which the SIL is located at an insertion position.

FIG. 18 is a bottom view showing the SIL manipulator and objective lensin a state in which the SIL is located at a replacement position.

FIG. 19 is a perspective view showing a configuration of an SIL holder.

FIG. 20 is a figure including vertical sectional views showing (a) astate of the SIL holder at the standby position and (b) a state of theSIL holder at the insertion position, respectively.

FIG. 21 is a configuration diagram of a semiconductor inspectionapparatus to which an embodiment of the solid immersion lens holder isapplied.

FIG. 22 is a configuration diagram showing a configuration of the solidimmersion lens holder.

FIG. 23 is an exploded perspective view of the solid immersion lensholder shown in FIG. 22.

FIG. 24 is a sectional view along line IV-IV in FIG. 23.

FIG. 25 is a bottom view of the solid immersion lens holder according tothe second embodiment.

FIG. 26 is a bottom view of the solid immersion lens holder according tothe third embodiment.

FIG. 27 is an exploded side view of the solid immersion lens holderaccording to the fourth embodiment.

FIG. 28 is a bottom view of the solid immersion lens holder according tothe fifth embodiment.

FIG. 29 is a sectional view along line IX-IX in FIG. 28.

FIG. 30 is an exploded perspective view of the solid immersion lensholder according to the sixth embodiment.

FIG. 31 is a view of the solid immersion lens holder of the seventhembodiment from the objective lens side.

FIG. 32 is a sectional view along line XII-XII in FIG. 31.

FIG. 33 is a view of the solid immersion lens holder shown in FIG. 32from a direction of arrow A2 in FIG. 32.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the microscope and the sample observationmethod according to the present invention will be described below indetail with reference to the drawings. In the description of drawingsthe same elements will be denoted by the same reference symbols, withoutredundant description. It is also noted that dimensional ratios in thedrawings do not always agree with those in the description.

First, a basic configuration of a semiconductor inspection apparatusbeing a microscope according to the present invention will be described.FIG. 1 is a block diagram schematically showing a configuration of anembodiment of the semiconductor inspection apparatus according to thepresent invention. The present apparatus is an inspection device adaptedfor a semiconductor device S, for example, in which a circuit patternconsisting of transistors, interconnections, etc. is formed on a devicesurface, as a sample of an inspected object (observed object), and isconfigured to set the device surface at an observation plane and observeto inspect the semiconductor device S through the substrate from theback side opposite the device surface. Here the microscope and sampleobservation method according to the present invention are applicable toany cases where the observation of the sample is carried out at thepredetermined observation plane and through the sample, but the presentinvention will be described below mainly about the semiconductorinspection apparatus and inspection method as an application examplethereof.

The semiconductor inspection apparatus in the present embodiment iscomprised of an observation part A for observation of the semiconductordevice S, a control part B for control of operations of respectiveportions in the observation part A, and an analysis part C forprocessing, instructions, etc. necessary for the inspection of thesemiconductor device S. The semiconductor device S as a sample of aninspected object, i.e., an observed object by the present inspectionapparatus is mounted on a stage 18 in the observation part A so that adevice surface as an observed surface thereof is placed on the stage 18side and so that the back surface is up.

The observation part A has an image acquisition part 1 housed in a blackbox (not shown), an optical system 2, and a solid immersion lens (SIL)3. The image acquisition part 1 is, for example, a means comprised of aphotodetector, an image pickup device, or the like and adapted toacquire an image of the semiconductor device S. The optical system 2 forguiding an image of light from the semiconductor device S to the imageacquisition part 1 is disposed between the image acquisition part 1, andthe semiconductor device S mounted on the stage 18.

The optical system 2 is provided with an objective lens 20 at apredetermined position opposite to the semiconductor device S, to whichthe light from the semiconductor device S is incident. Light, forexample, emerging from or reflected from the semiconductor device S isincident to the objective lens 20 and travels through the optical system2 including the objective lens 20, to the image acquisition part 1. Thenthe image acquisition part 1 acquires the image of the semiconductordevice S to be used in inspection.

The image acquisition part 1 and the optical system 2 are integrallyconstructed in a state in which their optical axes are coincident witheach other. An XYZ stage 15 consisting of an XY stage 15 a and a Z stage15 b is provided for these image acquisition part 1 and optical system2. The XY stage 15 a is used for moving the image acquisition part 1 andoptical system 2 in the X-Y plane (horizontal plane) to set theobservation position (inspection position) for the semiconductor deviceS. The Z stage 15 b is used for moving the image acquisition part 1 andoptical system 2 in the Z direction (vertical direction) to adjust thefocal point relative to the semiconductor device S. This permits the Zstage 15 b to function as a focusing means for changing the distancebetween the substrate of the semiconductor device S and the objectivelens 20 of the optical system 2 to effect focusing in observation.

In the present embodiment, as shown in the side sectional view of FIG.2, the objective lens 20 is composed of two lens units, first lens unit20 a and second lens unit 20 b. These lens units 20 a, 20 b are locatedon the upper side and on the lower side, respectively, along the opticalaxis of the objective lens 20. The objective lens 20 is so configuredthat a spacing u between the lens units 20 a and 20 b can be varied byrotating a correction ring 21 (cf. FIG. 1) provided in its peripheralpart. The correction ring 21 is controlled in driving by correction ringdriver 40. This permits the correction ring 21 and correction ringdriver 40 to function as an aberration correction means for effectingaberration correction in observation by changing the spacing u betweenthe lens units 20 a, 20 b in the objective lens 20.

In the configuration as described above, the focusing means comprised ofthe Z stage 15 b, and the aberration correction means comprised of thecorrection ring 21 and correction ring driver 40 constitute an objectivelens driving means for driving the objective lens 20 to effect thefocusing and aberration correction for the semiconductor device S. FIG.2 is depicted without illustration of a specific structure and drivingmechanism of the objective lens 20 including the correction ring 21. Itis also possible to drive the stage 18 carrying the semiconductor deviceS, in order to achieve the focusing for the semiconductor device S.

In the inspection apparatus shown in FIG. 1, an inspection part 16 isprovided for the semiconductor device S. In the inspection ofsemiconductor device S, the inspection part 16 performs control of astate of the semiconductor device S and others according to need. Thereare different methods of controlling the state of the semiconductordevice S by the inspection part 16, depending upon specific inspectionmethods applied to the semiconductor device S; for example, applicablemethods include a method of supplying a voltage to a predeterminedportion of a circuit pattern formed in the semiconductor device S, amethod of irradiating a laser beam as a probe beam to the semiconductordevice S, and so on.

In the present embodiment, SIL 3 is further disposed in this observationpart A. This SIL 3 is a lens used for magnifying the image of thesemiconductor device S. The SIL 3 is arranged movable relative to theimage acquisition part 1 and optical system 2 and relative to thesemiconductor device S mounted on the stage 18. Specifically, the SIL 3is arranged to be movable between an insertion position at which the SIL3 is placed so as to include the optical axis from the semiconductordevice S to the objective lens 20 and be kept in contact with thesemiconductor device S, and a standby position off the optical axis.

A solid immersion lens driver (SIL driver) 30 is provided for the SIL 3.The SIL driver 30 is a driving means for driving the SIL 3 to move itbetween the aforementioned insertion position and standby position. TheSIL driver 30 finely moves the location of SIL 3 to adjust the insertionposition of SIL 3 relative to the objective lens 20 of the opticalsystem 2. In FIG. 1, the SIL 3 is illustrated in a state in which it isplaced at the insertion position between the objective lens 20 and thesemiconductor device S.

Here the SIL is usually a lens of hemispherical shape with the focalpoint at the center of sphere effecting n-fold multiplication of thenumerical aperture NA and magnification, or a lens of hyperhemisphericalshape with the focal point at a position R/n below the center of sphere,effecting n²-fold multiplication of the numerical aperture NA andmagnification (e.g., cf. Japanese Patent Application Laid-Open No.2002-189000).

FIG. 3 is a side view showing an observation method of the semiconductordevice using the SIL in the inspection apparatus shown in FIG. 1. In thepresent inspection apparatus, as described above, the semiconductordevice S is placed on the stage 18 so that the device surface Sa thereofis down (on the stage 18 side) and the back surface Sb up (on theobjective lens 20 side). Relative to this semiconductor device S, theSIL 3 at the insertion position is placed so that its planar or convexlens surface is kept in close contact with the back surface Sb. Specificexamples of the SIL include such known lenses as plano-convex lenses andbi-convex lenses (e.g., reference should be made to Japanese PatentApplication Laid-Open No. H5-157701 and U.S. Pat. No. 6,594,086).

Where the semiconductor device S is observed from the back side Sbthrough the substrate by use of the objective lens 20 and SIL 3, theoptical parameters in the semiconductor device S include the refractiveindex n₀ and the thickness t₀ of the substrate. The optical parametersin the SIL 3 include the refractive index n₁, thickness d₁, andcurvature radius R₁ of the spherical lens surface. In FIG. 3, solidlines indicate optical paths traveling from the objective lens 20 sidethrough the SIL 3 and the substrate and focused on the device surfaceSa. In addition, dashed lines indicate optical paths on the assumptionthat the refractive index n₀ of the substrate of the semiconductordevice S would be equal to that n₁ of SIL 3.

In the same drawing L represents a depth of measurement from thespherical surface of the solid immersion lens, SIL 3 in the case of theoptical paths indicated by the dashed lines, i.e., a distance betweenthe focal point determined from the shape of the lens surface of SIL 3and the apex of SIL 3 (hereinafter referred to as a measurement depth).This measurement depth L is determined by L=d₁+t₀×(n₁/n₀) so as to setthe focal point on the device surface Sa in actual observation. Aspecific lens shape of the SIL 3 (e.g., setting of thickness d₁ tocurvature radius R₁) can be optionally set according to need. Ingeneral, as to the thickness t₀ of the substrate (sample), where theobservation is carried out at the observation plane set inside thesample and through part of the sample, the thickness of the sample up tothe observation plane can be set as the thickness t₀.

For the observation part A for carrying out the observation and othersfor inspection of the semiconductor device S, there are provided thecontrol part B and analysis part C.

The control part B has an observation controller 51, a stage controller52, an SIL controller 53, and an objective lens controller 54. Theobservation controller 51 controls operations of the image acquisitionpart 1 and inspection part 16, thereby controlling execution ofobservation of the semiconductor device S carried out in the observationpart A, setting of observation conditions, and so on.

The stage controller 52 controls the operation of XY stage 15 a, therebycontrolling setting of the observation position of the semiconductordevice S by the image acquisition part 1 and optical system 2 as aninspection position in the present inspection apparatus, or positioningthereof. The SIL controller 53 controls the operation of SIL driver 30,thereby controlling movement of the SIL 3 between the insertion positionand the standby position, or adjustment of the insertion position of SIL3, or the like.

The objective lens controller 54 controls the operation of the Z stage15 b, thereby controlling the focusing to change the distance betweenthe substrate of the semiconductor device S and the objective lens 20.Furthermore, this controller 54 controls the operations of thecorrection ring driver 40 and the correction ring 21, therebycontrolling the aberration correction to change the spacing u betweenthe lens units 20 a, 20 b in the objective lens 20.

The analysis part C has an image analyzer 61 and instructor 62. Theimage analyzer 61 performs a required analysis process and others forthe image acquired by the image acquisition part 1. The instructor 62gives necessary instructions for the control part B, with reference toinput contents from an operator, analysis contents by the image analyzer61, and so on. A display unit 63 is coupled to the analysis part C. Animage, data, or the like acquired or analyzed by the analysis part C isdisplayed on the display unit 63 as occasion may demand.

In this configuration, the control part B serves as a controlling meansfor controlling the objective lens driving means including the Z stage15 b, correction ring driver 40, and correction ring 21, and the solidimmersion lens driving means including the SIL driver 30, to control theobservation conditions in observation of the device surface Sa of thesemiconductor device S. In the present embodiment, particularly,corresponding to the configuration wherein the SIL 3 is movable betweenthe insertion position and the standby position, the control part Bincluding the SIL controller 53 and the objective lens controller 54 hastwo control modes, a normal mode (first mode) and a solid immersion lensmode (SIL mode or second mode).

In the normal mode, the SIL controller 53 makes the SIL driver 30 placethe SIL 3 at the standby position off the optical axis. The objectivelens controller 54 controls the Z stage 15 b, correction ring driver 40,and correction ring 21 to perform the focusing and aberration correctionin observation conditions, under a first correction condition set basedon the refractive index n₀ and thickness t₀ of the substrate of thesemiconductor device S. Then the observation of the semiconductor deviceS from the back side Sb is carried out through the optical system 2including the objective lens 20. The objective lens controller 54 isprovided with a first focusing table and a first aberration correctiontable corresponding to the first correction condition.

In the SIL mode, the SIL controller 53 makes the SIL driver 30 place theSIL 3 at the insertion position including the optical axis. Theobjective lens controller 54 controls the Z stage 15 b, correction ringdriver 40, and correction ring 21 to perform the focusing and aberrationcorrection in observation conditions, under a second correctioncondition set based on the refractive index n₀ and thickness t₀ of thesubstrate of the semiconductor device S, and the refractive index n₁,thickness d₁, and curvature radius R₁ of SIL 3. Then the observation ofthe semiconductor device S from the back side Sb is carried out throughthe optical system 2 including the objective lens 20, and through theSIL 3. The objective lens controller 54 is provided with a secondfocusing table and a second aberration correction table corresponding tothis second correction condition.

Next, a semiconductor inspection method, which is a sample observationmethod according to the present invention, will be described. FIG. 4 isa flowchart showing an example of the semiconductor inspection methodusing the inspection apparatus shown in FIG. 1. FIG. 5 is a flowchartspecifically showing observation methods by observation in the normalmode and observation in the SIL mode in the inspection method shown inFIG. 4. FIG. 6 is a figure including schematic diagrams showing (a) thedefault state, (b) the normal mode, and (c) the SIL mode in observationof a semiconductor device.

The first step is to select an SIL 3 having optical parameters suitablefor observation of the semiconductor device S as an inspected object andto set the SIL 3 on the SIL driver 30 (step S101). Then the opticalparameters of the refractive index n₁, thickness d₁, and curvatureradius R₁ of the selected SIL 3 are entered through an input deviceprovided in the analysis part C (S102). The semiconductor device S as aninspected object is set with its back side Sb up on the stage 18 (S103).Then the focal point of observation is matched with the back side Sb ofthe semiconductor device S thus set. This results in setting the focusand aberration so as to locate the focal point on the back side Sb beingthe top surface of the semiconductor device S, as shown in FIG. 6(a)(S104). This state, i.e., the thickness of substrate t₀=0 is the defaultstate (origin set state) in observation of the semiconductor device S.In this state the SIL 3 is positioned at the standby position off theoptical axis.

Next, the optical parameters of the refractive index n₀ and thickness t₀of the substrate of the semiconductor device S being a sample of anobserved object are entered (S105).

Subsequently, the semiconductor device S is observed in the normal modewith use of the objective lens 20 (S200). Specifically, as shown in theflowchart of FIG. 5, the movement amount ΔZ of the objective lens 20 andthe spacing u between lens units 20 a, 20 b are adjusted using the firstfocusing table and the first aberration correction table according tothe refractive index n₀ and the thickness t₀ of the substrate. Thisresults in executing the focusing and aberration correction so as tomatch the focal point with the device surface Sa set at the observationplane of the semiconductor device S and through the substrate from theback side Sb, as shown in FIG. 6(b) (S201, first correction step).

After completion of the setting of the observation conditions, anobservation for inspection of the semiconductor device S is carried out(S202, first image observation step). At this step, a normal image of acircuit pattern provided in the device surface Sa of the semiconductordevice S is observed through the optical system 2 containing theobjective lens 20, by the image acquisition part 1. The stage controller52 drives the XY stage 15 a to move the image acquisition part 1 andoptical system 2 in the X-Y plane. Then a portion to be observed in thesemiconductor device S is set at the center of the field of view and isspecified as an inspection position (observation position).

Subsequently, an observation is carried out in the SIL mode using theSIL 3 in addition to the objective lens 20 (S300). Specifically, the SILcontroller 53 drives the SIL driver 30 to move the SIL 3 from thestandby position to the insertion position. Then the SIL 3 is broughtinto the field so as to match the inspection position, in a state inwhich the SIL 3 is in close contact with the back side Sb of thesemiconductor device S (S301). In this state, the movement amount ΔZ ofthe objective lens 20, and the spacing u between lens units 20 a, 20 bare adjusted using the second focusing table and the second aberrationcorrection table according to the refractive index n₀ and thickness t₀of the substrate, and the refractive index n₁, thickness d₁, andcurvature radius R₁ of the SIL 3. This results in executing the focusingand aberration correction so as to match the focal point with the devicesurface Sa of the semiconductor device S through the SIL 3 and thesubstrate, as shown in FIG. 6(c) (S302, second correction step). Fineadjustment is carried out as to the observation conditions such as thefocal point, aberration, and the location of the SIL 3 as occasion maydemand (S303).

After completion of the setting of the observation conditions, theobservation of the semiconductor device S is carried out (S304, secondimage observation step). At this step, an enlarged image of thesemiconductor device S is observed through the optical system 2containing the objective lens 20, and through the SIL 3 by the imageacquisition part 1 to inspect a circuit pattern at the inspectionposition. After completion of the necessary observation and inspectionfor the set inspection position, the SIL 3 is moved out of the field tothe standby position (S305).

Then, whether it is necessary to observe another position is determinedfor the semiconductor device S set on the stage 18, as shown in theflowchart of FIG. 4 (S106). If necessary, the observation in the normalmode (S200) and the observation in the SIL mode (S300) are repeatedlycarried out. If there is no need for observation of another position, itis determined whether it is necessary to observe another semiconductordevice (S107). If necessary, the processes including the step of settingthe semiconductor device S (S103) and the steps thereafter arerepeatedly carried out. If there is no need for observation of anothersemiconductor device, the inspection of semiconductor device isterminated.

The effects of the semiconductor inspection apparatus and semiconductorinspection method in the present embodiment will be described below.

In the semiconductor inspection apparatus shown in FIG. 1 and in thesemiconductor inspection method shown in FIGS. 4 and 5, the inspectionof the semiconductor device S from the back side Sb through thesubstrate is carried out so as to implement the inspection with aswitchover between the normal mode of carrying out the observation withthe SIL 3 at the standby position and under the observation conditionstaking account of the optical parameters n₀, to of the substrate and theSIL mode of carrying out the observation with the SIL 3 at the insertionposition and under the observation conditions taking account of theoptical parameters n₀, to of the substrate and the optical parametersn₁, d₁, R₁ of the SIL 3. This makes it feasible to properly execute thefocusing and aberration correction in each of the present and absentstates of SIL 3 and to suitably acquire each of the normal image and theenlarged image of the semiconductor device S. Accordingly, it becomesfeasible to readily carry out the inspection such as the analysis ofmicrostructure of the semiconductor device S.

The above embodiment employs the Z stage 15 b to adjust the spacingbetween the substrate of the semiconductor device S and the objectivelens 20, as the focusing means for the objective lens 20. The aboveembodiment also adopts the lens configuration consisting of the lensunits 20 a, 20 b and the correction ring 21 and the correction ringdriver 40 for adjustment of the spacing between the lens units, as theaberration correction means for the objective lens 20. Thisconfiguration permits us to suitably adjust the focus and aberration inobservation of the semiconductor device S. It is also a matter of coursethat any configuration other than these may be used. For example, as tothe focusing for the semiconductor device S, it is also possible toadopt the configuration of driving the stage 18 carrying thesemiconductor device S in the Z-axis direction as described above.

The focusing and aberration correction are executed by the specificmethods using the focusing tables and aberration correction tablesprepared corresponding to the respective correction conditions in thecontrol part B. This implements easy and sure correction for theobservation conditions for the semiconductor device S. However, thefocusing and aberration correction can also be implemented by use of anyother method than the above methods using the focusing tables andaberration correction tables. For example, a potential configuration issuch that computational expressions necessary for focusing andaberration correction are prepared and conditions for focusing andaberration correction are calculated using the computationalexpressions.

In the configuration shown in FIG. 1, specifically, the focusing tablesare preferably prepared based on Z-directional driving distances (focusmovement amounts) ΔZ of the objective lens 20 by the Z stage 15 b. Theaberration correction tables are preferably prepared based on spacings ubetween lens units 20 a, 20 b in the objective lens 20 or based onamounts of rotation of the correction ring 21 corresponding to spacingsu.

These correction tables may be arranged as follows: tables arepreliminarily prepared in the number necessary for combinations ofoptical parameters of envisioned substrates and SILs and a table to beused is selected according to input parameters. Alternatively, acorrection table may be created at a point of time of entry ofparameters. The entry of the optical parameters of SIL can beimplemented by individually entering values of parameters, or by anyother method, for example, by a configuration of preparing a set ofparameters corresponding to each model number of SIL, by a configurationof providing each SIL with a storage medium such as an IC chip storingvalues of parameters, and retrieving the data at a time of use, and soon.

Listed below are principal materials to be used for the semiconductorsubstrate and SIL, and refractive indices n thereof.

Si: 3.5

GaP: 3.1

GaAs: 3.4

Glass: 1.45-2

Plastics: 1.45-2

The material of SIL is preferably selected as one with a refractiveindex close to that of the substrate material such as Si or GaP in thesemiconductor device as an inspected object. The above embodimentdescribed the semiconductor inspection apparatus and inspection methodfor the semiconductor device as a sample of an observed object, and ingeneral, where samples are a variety of devices such as thesemiconductor devices, the target devices do not have to be limited tothose using a semiconductor substrate, but observed objects may also beintegrated circuits using a substrate of glass, plastic, or the like,such as polysilicon thin-film transistors. For example, a device isfabricated on a glass substrate in the case of a liquid crystal device,and a device is fabricated on a plastic substrate in the case of anorganic EL device or the like.

Where the SIL used is one made of Si, it presents an advantage of noaberration at the interface between the substrate and the SIL if thesubstrate is an Si substrate. However, attention is needed in that thetransmittance is low for light of wavelengths of not more than 1.1 μMand the light is absorbed by the SIL even if the substrate is made thin.

Where the SIL used is one made of GaP, it presents an advantage of alsotransmitting light with wavelengths ranging from the visible to infraredregion, in addition to the wavelength region transmitted by Si. In thiscase, if the Si substrate has a thickness small enough, the observationcan be performed in such a wavelength region. For example, where the Sisubstrate has the thickness as thin as about 30 μm and where a laserbeam with the wavelength of not more than 1 μm is used in acquisition ofan image by LSM (described later), it is feasible to implementachievement of high resolution of observation. On the other hand,attention is needed in that the GaP SIL gives rise to geometricaberration like spherical aberration due to the index difference at theinterface between the substrate and the SIL in the case of the Sisubstrate. When the substrate is thin enough as described above, theeffect of geometric aberration can be ignored.

The semiconductor inspection method described above will be furtherdescribed with specific data.

First, the correction for the observation conditions in the normal modewill be described. In the observation of the device surface Sa of thesemiconductor device S with the objective lens 20 (cf. FIG. 6(b)), thegeometric aberration I appearing on the back side Sb of the substrate isgiven by Eq (1) below.I=(n ₀ ²−1)t ₀ NA ²/(2n ₀ ³)  (1)In this Eq (1), NA represents the numerical aperture of the objectivelens 20.

FIG. 7 is a graph showing an example of correlation between refractiveindex of substrate and geometric aberration. In this graph, thehorizontal axis represents the refractive index n₀ of the substrate(sample) as an observed object, and the vertical axis (geometricaberration/thickness of substrate) I/t₀. In this graph, the numericalaperture of the objective lens 20 is assumed to be NA=0.76. In thecorrection for the observation conditions in the normal mode, thefocusing table and aberration correction table are prepared based on theoptical characteristics such as the geometric aberration I determined inthis way.

FIG. 8 is a graph showing an example of correlation between thickness ofsubstrate and focus movement amount of movement of the objective lens.In this graph, the horizontal axis represents the thickness t₀ (μm) ofthe substrate, and the vertical axis the focus movement amount ΔZ (mm).Graph A1 indicates a correlation in the case of the substrate materialof Si (n₀=3.5), graph A2 that in the case of the substrate material ofGaP (n₀=3.1), and graph A3 that in the case of the substrate material ofglass (n₀=1.5). As apparent from Eq (1), if NA and n₀ are constant, thegeometric aberration I is proportional to the thickness t₀ of thesubstrate. In the example shown in FIG. 8, therefore, the focus movementamount ΔZ for focusing can be calculated by a proportional expression tothe thickness t₀ or the geometric aberration I.

FIG. 9 is a graph showing an example of correlation between thickness ofsubstrate and spacing between lens units in the objective lens. In thisgraph, the horizontal axis represents the thickness t₀ (μm) of thesubstrate, and the vertical axis the spacing u (mm) between lens units20 a, 20 b set in the objective lens 20. Graph B1 indicates acorrelation in the case of the substrate material of Si, graph B2 thatin the case of the substrate material of GaP, and graph B3 that in thecase of the substrate material of glass. In the example shown in FIG. 9,the spacing u between lens units for aberration correction can becalculated by a linear expression to the thickness t₀ or the geometricaberration I. In FIGS. 8 and 9, specific correlation equations includingcoefficient values and others are determined by a lens configuration ofeach objective lens 20 or the like. A function system including theorder of the correlation equations and others can be optionallydetermined out of appropriate systems.

Next, the correction for the observation conditions in the SIL mode willbe described. In the observation of the device surface Sa with the SIL 3in addition to the objective lens 20 (cf. FIG. 6(c)), the geometricaberration I amounts to the sum I=I1+I2 of the geometric aberration I1appearing at the lens spherical surface of SIL 3 and the geometricaberration I2 appearing at the interface between SIL 3 and thesubstrate. The geometric aberration I1 appearing at the lens sphericalsurface of SIL 3 is given by Eq (2) below, supposing R₁=1 mm and n₁=3.5for simplicity.I1=6.25(L−1)²×(3.5 L−4.5)L  (2)In this Eq (2), L represents the measurement depth of SIL 3 shown inFIG. 3.

The geometric aberration I2 appearing at the interface between SIL 3 andthe substrate is given by Eq (3) below.I2=n ₁(n ₀ ² −n ₁ ²)t ₀ NA ²/(2n ₀ ³)  (3)In the correction for the observation conditions in the SIL mode, thefocusing table and aberration correction table are prepared based on theoptical characteristics such as the geometric aberrations I1, I2determined in this way.

FIG. 10 is a graph showing an example of correlation between measurementdepth and focus movement amount. In this graph, the horizontal axisrepresents the measurement depth L (μm), and the vertical axis the focusmovement amount ΔZ (mm). In this graph, the optical parameters of thesubstrate are set as n₀=3.5 and t₀=100 μM, and the optical parameters ofthe SIL 3 as n₁=3.1 and R₁=0.5 mm. The thickness d₁ of SIL 3 varies withthe measurement depth L according to the aforementioned equation ofL=d₁+t₀×(n₁/n₀). The focus movement amount ΔZ for focusing is calculatedby the correlation as shown in this FIG. 10.

FIG. 11 is a graph showing an example of correlation between measurementdepth and spacing between lens units in the objective lens. In thisgraph, the horizontal axis represents the measurement depth L (μm), andthe vertical axis the spacing u (mm) between lens units 20 a, 20 b. Thisgraph shows corrected states where the optical parameter of thesubstrate is n₀=3.5, the optical parameters of the SIL 3 are n₁=3.1 andR₁=0.5 mm, and attained NA is 2.2. Graph C0 indicates a state withoutcorrection, graph C1 a corrected state at the thickness d₁=480 μm of SIL3, C2 that at d₁=450 μm, C3 that at d₁=420 μm, C4 that at d₁=390 μm, C5that at d₁=360 μm, and C6 that at d₁=330 μm. The thickness t₀ of thesubstrate varies with the measurement depth L according to theaforementioned equation of L.

FIG. 12 is a graph showing another example of correlation betweenmeasurement depth and spacing between lens units in the objective lens.This graph shows a corrected state where the optical parameter of thesubstrate is n₀=3.5, the optical parameters of SIL 3 are n₁=3.5 andR₁=0.5 mm, and attained NA is 2.5. In this case, since the substrate andSIL 3 have the same refractive index, the spacing u between lens unitsis not dependent upon the thickness d₁ of SIL 3, but the thickness t₀ ofthe substrate and the thickness d₁ of SIL 3 vary in arbitrarycombination with the measurement depth L. The spacing u between lensunits for aberration correction is calculated by these correlations asshown in FIGS. 11 and 12.

The semiconductor inspection apparatus and inspection method accordingto the present invention will be further described below.

FIG. 13 is a configuration diagram showing another embodiment of thesemiconductor inspection apparatus according to the present invention.FIG. 14 is a configuration diagram showing a side view of thesemiconductor inspection apparatus shown in FIG. 13. The presentembodiment is an example showing a specific configuration of thesemiconductor inspection apparatus shown in FIG. 1.

The semiconductor inspection apparatus in the present embodiment isprovided with an observation part A, a control part B, and an analysispart C. Here the analysis part C is omitted from the illustration. Asemiconductor device S as an inspected object is mounted on a stage 18provided in the observation part A. Furthermore, in the presentembodiment, the apparatus is equipped with a test fixture 19 forapplying an electric signal necessary for inspection or the like to thesemiconductor device S. The semiconductor device S is placed with itsback side facing the objective lens 20.

The observation part A has a high-sensitivity camera 10 set in a blackbox (not shown), a laser scan optic (LSM: Laser Scanning Microscope)unit 12, optical systems 22, 24, an XYZ stage 15, an SIL 3, an SILdriver 30, and a correction ring driver 40.

Among these components, the camera 10 and LSM unit 12 correspond to theimage acquisition part 1 in the configuration shown in FIG. 1. Theoptical systems 22, 24 correspond to the optical system 2. An objectivelens 20 is located on the semiconductor device S side of the opticalsystems 22, 24. In the present embodiment, as shown in FIGS. 13 and 14,a plurality of objective lenses 20 having their respectivemagnifications different from each other are arranged to be switchablefrom one to another. An objective lens 20 is provided with two lensunits 20 a, 20 b and a correction ring 21 as shown in FIG. 2 and isconfigured to be able to correct aberration by the correction ringdriver 40. The test fixture 19 corresponds to the inspection part 16.The LSM unit 12 also has the function of the inspection part 16 inaddition to the function of the image acquisition part 1.

The optical system 22 is a camera optical system for guiding light fromthe semiconductor device S incident through the objective lens 20, tothe camera 10. The camera optical system 22 has an imaging lens 22 a forfocusing an image magnified at a predetermined magnification by anobjective lens 20, on a light receiving surface inside the camera 10. Abeam splitter 24 a of the optical system 24 is interposed betweenobjective lens 20 and imaging lens 22 a. The high-sensitivity camera 10can be, for example, a cooled CCD camera or the like.

In this configuration, the light from the semiconductor device S isguided through the optical system including the objective lens 20 andthe camera optical system 22 to the camera 10. Then the camera 10 picksup an image such as a pattern image of the semiconductor device S. Inanother configuration, the camera can also picks up an emission image ofthe semiconductor device S. In this case, light emitted from thesemiconductor device S in a voltage applied state by the test fixture 19is guided through the optical system to the camera 10. Then the camera10 picks up the emission image of the semiconductor device S to be usedas an abnormality observation image. Specific examples of the emissionfrom the semiconductor device S include one due to an abnormal portionbased on a defect of the semiconductor device, transient emission withswitching operation of a transistor in the semiconductor device, and soon. Furthermore, the acquired image may be an exothermic image based ona defect of device.

The LSM unit 12 has a laser beam introduction optical fiber 12 a forirradiating an infrared laser beam, a collimator lens 12 b forcollimating the laser beam irradiated from the optical fiber 12 a, intoa parallel beam, a beam splitter 12 e for reflecting the laser beamcollimated into the parallel beam by the lens 12 b, to change theoptical path, and an XY scanner 12 f for moving the laser beam reflectedby the beam splitter 12 e, in the XY directions to emit the laser beamtoward the semiconductor device S.

The LSM unit 12 also has a condenser lens 12 d for condensing lighthaving been injected through the XY scanner 12 f from the semiconductordevice S side and having passed through the beam splitter 12 e, and adetection optical fiber 12 c for detecting the light condensed by thecondenser lens 12 d.

The optical system 24 is an LSM unit optical system for guiding lightbetween the semiconductor device S and objective lens 20 and, the XYscanner 12 f of the LSM unit 12. The LSM unit optical system 24 has abeam splitter 24 a for reflecting part of light having been injectedfrom the semiconductor device S through the objective lens 20, a mirror24 b for changing the optical path of the light reflected by the beamsplitter 24 a, to the optical path toward the LSM unit 12, and a lens 24c for condensing the light reflected by the mirror 24 b.

In this configuration, the infrared laser beam emitted from a laserlight source (not shown) and guided through the laser beam introductionoptical fiber 12 a travels via the lens 12 b, beam splitter 12 e, XYscanner 12 f, optical system 24, and objective lens 20 onto thesemiconductor device S and then enters the interior of the semiconductordevice S.

Reflectively scattered light from the semiconductor device S withincidence of the incident light reflects a circuit pattern provided inthe device surface of the semiconductor device S. The reflected lightfrom the semiconductor device S travels through the optical pathopposite to the incident light to reach the beam splitter 12 e, and thenpasses through the beam splitter 12 e. The light through the beamsplitter 12 e then travels through the lens 12 d to enter the detectionoptical fiber 12 c, and is detected by a photodetector coupled to thedetection optical fiber 12 c.

The intensity of the light detected through the detection optical fiber12 c by the photodetector is the intensity reflecting the circuitpattern provided in the semiconductor device S, as described above.Accordingly, while the infrared laser beam scans the semiconductordevice S on the X-Y plane by the XY scanner 12 f, a sharp image of thecircuit pattern of the semiconductor device S or the like can be pickedup.

The observation part A is further provided with the SIL 3. The SIL 3 isarranged movable between the aforementioned insertion position andstandby position, relative to the high-sensitivity camera 10, LSM unit12, optical systems 22, 24, and objective lens 20 and relative to thesemiconductor device S mounted on the stage 18. The SIL driver 30 isprovided for the SIL 3. The SIL driver 30 is comprised of an SIL movingdevice (SIL manipulator) to which an SIL holder for supporting the SIL 3is coupled, and is an XYZ driving mechanism for moving the SIL 3 in theX, Y, and Z directions.

The control part B and analysis part C are provided for the observationpart A for carrying out the observation and others for inspection of thesemiconductor device S. In FIGS. 13 and 14, the analysis part C isomitted from the illustration.

The control part B has a camera controller 51 a, an LSM controller 51 b,an OBIRCH controller 51 c, a stage controller 52, an SIL controller 53,and an objective lens controller 54. Among these, the stage controller52, SIL controller 53, and objective lens controller 54 are as thosedescribed with FIG. 1, including the controls of focusing and aberrationcorrection in the two control modes. The camera controller 51 a, LSMcontroller 51 b, and OBIRCH controller 51 c correspond to theobservation controller 51 in the configuration shown in FIG. 1.

The camera controller 51 a and the LSM controller 51 b control theoperations of the high-sensitivity camera 10 and the LSM unit 12,respectively, thereby controlling the acquisition of an image ofsemiconductor device S carried out in the observation part A. The OBIRCHcontroller 51 c is provided for acquiring an OBIRCH (Optical BeamInduced Resistance Change) image used in inspection of the semiconductordevice S, and extracts a current change in the semiconductor device Sappearing during a scan with the laser beam.

The analysis part C, as shown in FIG. 1, has an image analyzer 61 and aninstructor 62, and is constructed, for example, of a computer or thelike. Image information from the camera controller 51 a and from the LSMcontroller 51 b is entered through an image capture board provided inthe computer of analysis part C.

A semiconductor inspection method with the semiconductor inspectionapparatus shown in FIGS. 13 and 14 will be schematically described (cfFIGS. 4 and 5). First, an observation of the semiconductor device S iscarried out under the observation conditions after completion of thefocusing and aberration correction in the first correction condition, inthe normal mode in which the SIL 3 is located at the standby position(S200). Specifically, the semiconductor device S is scanned by the LSMunit 12 to acquire a pattern image thereof. An abnormality observationimage used in detection of an abnormal portion in the semiconductordevice S is also acquired. Specific examples of this abnormalityobservation image include an OBIRCH image acquired by the OBIRCHcontroller 51 c, an emission image acquired by the camera 10, and so on.These pattern image and abnormality observation image are superimposedon each other, are displayed on the display device 63, etc. as occasionmay demand. The acquired images are used to check an abnormal portion inthe semiconductor device S, an abnormal portion detected is set as aninspection position, and the XYZ stage 15 and others are set so that theinspection position is located at the center of the field.

Then an observation of the semiconductor device S is carried out underthe observation conditions after completion of the focusing andaberration correction in the second correction condition, in the SILmode in which the SIL 3 is located at the insertion positioncorresponding to the inspection position of the semiconductor device S(S300). At this step, an enlarged pattern image, and an image such as anOBIRCH image or an emission image are acquired through the SIL 3 placedon the semiconductor device S and through the objective lens 20 andothers. Superposition of the images, display thereof on the displaydevice 63, etc. are carried out as occasion may demand. In acquisitionof an emission image, the stage and others are properly moved so as tomatch the amount of chromatic aberration caused by the SIL 3, and themagnification is adjusted by software to implement superposition ofimages.

We will now explain a specific example of the solid immersion lensmoving device (SIL moving device) used as the SIL driver 30 in thesemiconductor inspection apparatus shown in FIGS. 13 and 14. FIG. 15 isa perspective view from above an SIL manipulator as an SIL movingdevice, and the objective lens.

The SIL 3 is supported by SIL holder 5. The SIL manipulator 30A (SILdriver 30) shown in FIG. 15 is an SIL moving device for driving the SIL3 in the supported state by the SIL holder 5 in the three-dimensionaldirections to move the SIL 3 between the insertion position where theSIL 3 includes the optical axis to the objective lens 20 and is kept inclose contact with the semiconductor device S, and the standby positionoff the optical axis. The SIL manipulator 30A in the presentconfiguration example is further arranged to be also movable to areplacement position for replacement of the SIL 3 supported on the SILholder 5.

Specifically, the SIL manipulator 30A has a first arm member 71 equippedwith the SIL holder 5, a first arm member rotation source 72 forrotating the first arm member 71 in the X-Y plane (horizontal plane), asecond arm member 73 for holding the first arm member rotation source72, and a second arm member rotation source 74 for rotating the secondarm member 73 in the X-Y plane. Furthermore, the SIL manipulator 30A hasa Z-directional movement source 75 for moving the second arm memberrotation source 74 in the Z direction perpendicular to the X-Y plane,this Z-directional movement source 75 is placed on the base end side,and the moving first arm member 71 is located on the terminal end side.

The Z-directional movement source 75 is comprised of a Z-axis motor orthe like for moving a moving shaft in the Z direction, for example, by afeed screw or the like, and is mounted through a support portion 76 onthe microscope part on the main body side of the inspection apparatus.This support portion 76 is detachably attached to the main body of theapparatus, for example, by screwing or the like, so as to achieveconvenience in observation without the SIL manipulator 30A, inobservation with another SIL moving device, and so on. The second armmember rotation source 74 is coupled through a support portion 77 to themoving shaft of the Z-directional movement source 75. This second armmember rotation source 74 is comprised, for example, of a motor with anoutput shaft being a rotational shaft to rotate in forward and backwarddirections (which can be arranged to rotate within a predeterminedrange), and is moved in the Z direction with driving of theZ-directional movement source 75.

One end of the second arm member 73 is coupled to the rotational shaftof the second arm member rotation source 74. This second arm member 73is constructed in such curved shape that the second arm member 73 canreadily recede from the field of the observation position of thesemiconductor device S (the field of objective lens 20), as shown inFIG. 15. The first arm member rotation source 72 is fixed to the otherend of this second arm member 73. This first arm member rotation source72 is comprised, for example, of a motor with an output shaft being arotational shaft to rotate in forward and backward directions (which canbe arranged to rotate within a predetermined range).

As described above, the rotational shaft of the first arm memberrotation source 72 is so located as not to be coaxial with therotational shaft of the second arm member rotation source 74. Withdriving of the second arm member rotation source 74, the first armmember rotation source 72 is rotated together with the second arm member73 in the X-Y plane and about a fulcrum at the rotational shaft of thesecond arm member rotation source 74. The other end of theaforementioned first arm member 71 is coupled to the rotational shaft ofthe first arm member rotation source 72. This first arm member 71 isrotated in the X-Y plane and about a fulcrum at the rotational shaft ofthe first arm member rotation source 72, with driving of the first armmember rotation source 72.

In the above configuration, with driving of the first arm memberrotation source 72 and the second arm member rotation source 74, the SIL3 supported on the SIL holder 5 coupled to one end of the first armmember 71 is moved in a resultant direction of combination of theirrespective rotations in the X-Y plane. The SIL 3 is moved in the Zdirection by driving of the Z-directional movement source 75. As aconsequence, the SIL 3 is freely moved to any desired position in thethree-dimensional directions. FIGS. 16 to 18 are bottom views eachshowing the SIL manipulator 30A and the objective lens 20, wherein FIG.16 shows a state in which the SIL 3 is located at the standby position,FIG. 17 a state in which the SIL 3 is located at the insertion position,and FIG. 18 a state in which the SIL 3 is located at the replacementposition.

The SIL manipulator 30A shown in FIG. 15 is provided with an opticalcoupling material supply pipe 85 for supplying an optical contact liquidto the SIL 3, and a gas supply pipe 95 for supplying a drying gas. Theseare used on the occasion of placing the SIL 3 at the insertion positionand optically contacting the SIL 3 to the semiconductor device S.

The SIL holder 5 for supporting the SIL 3 will be described. FIG. 19 isa perspective view showing a configuration of the SIL holder in the SILmanipulator shown in FIG. 15. FIG. 20 is a figure including verticalsectional views showing (a) a state of the SIL holder at the standbyposition and (b) a state of the SIL holder at the insertion position,respectively.

The SIL holder 5, as shown in FIG. 19, is provided with a holder 6 ofnearly cylindrical shape for supporting the SIL 3, and an arm 7 forholding this holder 6. Since this SIL holder 5 can get into touch withthe optical contact liquid, it is made of a material highly resistant tocorrosion, for example, one of metals such as stainless steel, aluminum,etc., or a resin easy to be molded according to the lens shape, forexample, acrylic resin, PET, polyethylene, polycarbonate, and so on.

The holder 6, as shown in FIGS. 20(a) and 20(b), is provided with afirst holder 8 for holding the SIL 3, and a second holder 9 forsupporting this first holder 8. These first holder 8 and second holder 9are constructed in such nearly cylindrical shape as not to interferewith the optical path to the semiconductor device S.

The first holder 8 has an annular flange 8 a projecting outward from theperipheral surface in the upper part thereof, and also has an annularflange 8 b projecting inward in the bottom surface thereof. Then the SIL3 is fixed and held on the first holder 8, for example, with an adhesiveor the like in a state in which the bottom surface of the SIL 3 projectsdownward through an aperture formed in the inner circumference of theannular flange 8 b. The second holder 9 has an annular flange 9 aprojecting inward in the bottom surface thereof. The annular flange 8 aof the first holder 8 is mounted on the annular flange 9 a of the secondholder 9 in a state in which the bottom part of the first holder 8projects downward through an aperture 9 b formed in the innercircumference of the annular flange 9 a, and the first holder 8 and SIL3 are supported in the direction of weight on the second holder 9.

Since the dimensions are set in the relation of A<C<B herein where Arepresents the outside diameter of the lower part of the first holder 8,B the outside diameter of the annular flange 8 a of the first holder 8,and C the inside diameter of the aperture 9 b of the second holder 9,the first holder 8 is free relative to the second holder 9 and the firstholder 8 is prevented from dropping off downward from the second holder9.

The second holder 9 is provided with a cap 11 for retaining the SIL 3,which is mounted, for example, by fitting, meshing, or the like in anaperture 9 c in the upper part thereof. This cap 11 is constructed innearly cylindrical shape as the first holder 8 and the second holder 9are, and dimensions are set in the relation of D<B where D representsthe inside diameter of the cap 11. Accordingly, this cap 11 does notinterfere with the optical path to the semiconductor device S, andprevents the first holder 8 holding the SIL 3 from dropping off, e.g.,from jumping out through the aperture 9 c in the upper part of thesecond holder 9, thereby preventing loss of the SIL.

The arm 7 is constructed by bending a round bar in nearly L-shape toextend outward from the second holder 9, one end thereof projectsupward, and the other end is fixed to the side part of the second holder9. At one end of this arm 7, an antirotation portion 7 a, which containsa flat surface in part of a side face of a pipe, is fixed, for example,by fitting or the like so as to serve as a portion for preventingrotation of the arm 7 and holder 6. The arm 7 herein is constructed innearly L-shape to extend upward at one end thereof, but it may also beconstructed to extend within the X-Y plane. The arm 7 forming this SILholder 5 is detachably coupled to one end of the first arm member 71 inthe SIL manipulator 30A, as shown in FIG. 15.

In the SIL holder 5 and SIL manipulator 30A in the above configuration,the arm members 71, 73 are retracted in the state at the standbyposition shown in FIG. 16, so that the SIL 3 and arm members 71, 73 areoutside the field of the objective lens 20. At this time, the firstholder 8 holding the SIL 3 is in a state in which the annular flange 8 athereof is mounted on the annular flange 9 a of the second holder 9 andin which the first holder 8 and SIL 3 are supported in the direction ofweight on the second holder 9, as shown in FIG. 20(a).

When the SIL 3 is moved from this standby position to the insertionposition, the arm members 71, 73 are first rotated to move the SIL 3 atthe standby position to the position including the optical axis betweenthe semiconductor device S and the objective lens 20, as shown in FIG.17. At this time, since the second arm member 73 is constructed incurved shape, the second arm member 73 is readily located away from thefield, without interfering with the field of the objective lens 20.

After the SIL 3 is brought into the field in this way, the Z-directionalmovement source 75 of the SIL manipulator 30A is driven to lower the SIL3. When the SIL 3 is located near the observation position, the opticalcontact liquid is supplied through the optical coupling material supplypipe 85 and the SIL 3 is mounted on the observation position to beplaced at the contact position (insertion position). When the SIL 3 ismounted at the insertion position on the semiconductor device S, the SIL3 and first holder 8 supported in the direction of weight by the secondholder 9 go into a lifted state by the semiconductor device S, as shownin FIG. 20(b). Furthermore, fine adjustment or the like for the positionof the SIL 3 or the like is carried out in this state. An opticalcoupling material to be suitably used on this occasion can be an indexmatching fluid such as an index matching oil, or an optical contactliquid containing amphipathic molecules.

Since the SIL 3 and first holder 8 are free relative to the secondholder 9 in the lifted state by the semiconductor device S, only theweight of the SIL 3 and first holder 8 acts at the observation positionof the semiconductor device S. This prevents an excessive pressure frombeing applied to the semiconductor device, and the SIL 3 closely fitsthe semiconductor device at the observation position. Furthermore, thegas is supplied through the gas supply pipe 95 to dry the opticalcontact liquid, whereby the SIL 3 can be quickly and surely adhered tothe semiconductor device S at the observation position.

For replacing the SIL 3 with another, the first arm member rotationsource 72 of the SIL manipulator 30A is driven to rotate the first armmember 71, thereby moving the SIL 3 from the standby position to thereplacement position shown in FIG. 18 and largely projecting thecoupling part from near the position below the second arm member 73 tothe outside. Then the SIL holder 5 with the arm 7 is replaced withanother. This facilitates attachment and detachment of the arm 7 of theSIL holder 5 to and from the first arm member 71, and allows the SILholder 5 together with the arm 7 to be replaced with another, wherebythe lens replacement can be readily carried out without need fordirectly handling the small SIL 3.

The microscopes and sample observation methods according to the presentinvention are not limited to the above-described embodiments andconfiguration examples, but can be modified in various ways. Forexample, as to the specific configurations of the image acquisition part1, optical system 2, inspection part 16, etc. in the above-statedsemiconductor inspection apparatus and as to the specific inspectionmethods and others for inspection of the semiconductor device S, FIG. 13and FIG. 14 show just an example of the configurations, but it is alsopossible to adopt a variety of configurations and inspection methodsexcept for those. Where only the observation is carried out for variousdevices such as semiconductor devices, the apparatus may be constructedas a device observation apparatus without the inspection part 16. Theimage acquisition part 1 may also be excluded if not necessary, e.g.,where the operator directly observes the image. The SIL driver 30 fordriving the SIL 3 can also be implemented by a variety of mechanismsother than the SIL manipulator 30A shown in FIG. 15. It is also notedthat the use of the above optical coupling material for achieving theoptical contact between the SIL and the substrate is just an example,and another applicable method is to press the SIL against the substrateto achieve evanescent coupling.

The above embodiments described the semiconductor inspection apparatusand semiconductor inspection methods for the semiconductor device as anobserved object, but the present invention can also be applied to caseswhere an observed object except for the semiconductor devices is used asa sample, as a microscope and a sample observation method used forobservation of the sample at the predetermined observation plane andthrough the sample. This permits us to readily carry out the observationof the microstructure of the sample or the like in the observation ofthe sample. Specific examples of the sample in this case include, forexample, various devices such as the aforementioned semiconductordevices and liquid crystal devices, or bio-related samples using a slideor the like.

The entry of the optical parameters of SIL for the correction tables canbe implemented by individually entering values of parameters, or by anyother method, for example, by a configuration of preparing a set ofparameters corresponding to each model number of SIL, by a configurationof providing each SIL with a storage medium such as an IC chip storingvalues of parameters, and retrieving the data at a time of use, and soon, as described above.

For example, the entry of the optical parameters of SIL can beimplemented by a configuration of providing the SIL, SIL holder, or armwith a storage medium of a semiconductor device, magnetic device, or thelike, storing values of parameters such as a model number, serialnumber, curvature radius, thickness, and refractive index. Specificexamples of the method for retrieving the parameter data in thisconfiguration include a method of receiving the data by radio wave, amethod of receiving the data via electric contact through the arm andSIL manipulator, and the like. Alternatively, a configuration ofproviding the SIL holder with a bar code, and reading the parameter databy image recognition of the bar code can be used.

In addition, a configuration of providing the SIL holder with a mark forrecognizing the individual SIL with the naked eye or by using the imagecan be used. Specific examples of the method for retrieving theparameter data by using the above-mentioned mark include a method ofreading the data by using a number or color of lines, points, color ofthe holder itself, serial number, or the like. In this case, it ispossible to use a method of recognizing ID of the SIL by the mark,specifying the serial number, and retrieving the parameter data such asa curvature radius, thickness, and refractive index registered in thesoftware. The above parameter data corresponding to the SIL serialnumber can be provided by a flexible disk or the like, and registeredbeforehand in the software.

Further, in the microscope of the above configuration, the SIL is drivenby the solid immersion lens driving means, however, the microscope canbe configured without the solid immersion lens driving means, if it isunnecessary. In this case, the controlling means for controlling theobjective lens driving means may be configured to have at least the SILmode, as the control mode, in which the focusing and aberrationcorrection are carried out under the correction condition set based on arefractive index n₀ of the sample and a thickness t₀ of the sample up tothe observation plane, and a refractive index n₁, a thickness d₁, and aradius of curvature R₁ of the solid immersion lens.

In the above embodiments, the focusing and aberration correction arecarried out respectively in the normal mode and the SIL mode. However,as for the normal mode only with the objective lens, the focusing may becarried out without the aberration correction in the normal mode. Inthis case, if the correction tables are used in the normal mode, thecontrolling means may be configured to comprise only the focusing tablefor the normal mode, and without the aberration correction table.

As to the optical system 2 including the objective lens 20, it ispossible to adopt a variety of configurations in addition to the aboveconfigurations. For example, the optical system 2 may be configured tohave, as the objective lens 20, a first objective lens for observing anormal image of the sample in the normal mode, and a second objectivelens for observing an enlarged image of the sample with the SIL 3 in theSIL mode.

A specific example of such a configuration is that, in the case that aplurality of objective lenses 20 are arranged to be switchable by usinga revolver as shown in FIG. 13, one of these objective lenses is used asthe objective lens for the normal mode, and another objective lens towhich the SIL 3 is attached is used as the objective lens for the SILmode. In this configuration, the revolver for switching the objectivelenses functions as the solid immersion lens driving means. Further, inthe above case, an objective lens without a correction ring (cf FIGS. 1and 2) can be used as the objective lens for the normal mode, if theaberration correction is unnecessary.

An example of a sample observation method in the case of using thedifferent objective lenses in the normal mode and the SIL mode will bedescribed. First, a treatment with a washing liquid and contact liquidis carried out for improving the close contact characteristics of thesample surface, and then, the pattern image of the normal image of thesample is observed by using the normal objective lens. In addition, theabnormality observation image (for example the optical image due to thedefect) is observed. Subsequently, a portion to be observed is set atthe center, and the pattern image and the abnormality observation imageare similarly observed with the normal objective lens with a highermagnification. Further, the magnification of the objective lens israised up to about ×20, and the observation position is set at thecenter.

Next, the optical system is moved slightly away from the sample, theobjective lens is switched into the objective lens to which the SIL isattached, and then, the optical system is slowly moved to the sampleside. When the front end of the SIL comes in contact with the sample, acontact sensor is brought into ON state, and SIL is moved from the ONposition to the actual focus position. Here, a distance from the ONposition to the actual focus position is previously set.

Further, a fine adjustment of the focusing condition is carried out withobserving the pattern image of the sample by using the SIL-attachedobjective lens, and then, the pattern image and the abnormalityobservation image of the enlarged images of the sample are observed.Here, in the case that the observation of the normal image is againcarried out, the optical system is moved away from the sample, theobjective lens is switched into the normal objective lens, and then theoptical system is moved to the focus position.

The microscope described above is configured as a microscope forobserving a sample at a predetermined observation plane, comprising: (1)an optical system comprising an objective lens and adapted to guide animage of the sample; (2) objective lens driving means for driving theobjective lens to achieve focusing and aberration correction for thesample; (3) a solid immersion lens arranged at a position including anoptical axis from the sample to the optical system; and (4) controllingmeans for controlling the objective lens driving means, wherein (5) thecontrolling means has a solid immersion lens mode, as a control mode, inwhich the focusing and aberration correction are carried out under acorrection condition set based on a refractive index n₀ of the sampleand a thickness t₀ of the sample up to the observation plane, and arefractive index n₁, a thickness d₁, and a radius of curvature R₁ of thesolid immersion lens.

The sample observation method described above is configured as a sampleobservation method of observing a sample at a predetermined observationplane and through an optical system comprising an objective lens, thesample observation method comprising: (a) a correction step of placing asolid immersion lens at an insertion position including an optical axisfrom the sample to the optical system and carrying out focusing andaberration correction under a correction condition set based on arefractive index n₀ of the sample and a thickness t₀ of the sample up tothe observation plane, and a refractive index n₁, a thickness d₁, and aradius of curvature R₁ of the solid immersion lens; and (b) an enlargedimage observation step of observing an enlarged image of the sample in astate after completion of the focusing and aberration correction in thecorrection step.

Here, the microscope may be configured to comprise solid immersion lensdriving means for driving the solid immersion lens to move the solidimmersion lens between an insertion position including an optical axisfrom the sample to the optical system and a standby position off theoptical axis. Using the solid immersion lens driving means makes itfeasible to readily acquire the normal image/the enlarged image in theabsence/in the presence of the solid immersion lens, respectively.Further, the sample observation method may be configured to comprise anormal image observation step of observing a normal image of the samplein a state of placing the solid immersion lens at a standby position offthe optical axis.

Further, the optical system may be configured to have, as the objectivelens, a first objective lens for observing a normal image of the sample,and a second objective lens for observing an enlarged image of thesample with the solid immersion lens. In the configuration with thedifferent objective lenses for the observations in the absence/in thepresence of the solid immersion lens, a revolver for switching theobjective lenses functions as the above solid immersion lens drivingmeans.

In addition, it is preferable that, in the microscope, the controllingmeans has two control modes, a normal mode in which the focusing iscarried out by changing a distance between the sample and the objectivelens, and the solid immersion lens mode. Further, the microscope ispreferably configured so that in the normal mode, the focusing iscarried out under a normal correction condition set based on therefractive index n₀ of the sample and the thickness t₀ of the sample upto the observation plane. Similarly, it is preferable that the sampleobservation method comprises a normal correction step of placing thesolid immersion lens at the standby position off the optical axis fromthe sample to the objective lens and carrying out focusing by changing adistance between the sample and the objective lens. Further, the sampleobservation method is preferably configured so that in the normalcorrection step, the focusing is carried out under a normal correctioncondition set based on the refractive index n₀ of the sample and thethickness t₀ of the sample up to the observation plane. In the normalmode, the aberration correction may be carried out in addition to thefocusing if necessary, as in the solid immersion lens mode.

The microscope and sample observation method described above areconfigured to perform the observation of the sample on the basis of aswitchover between the first mode (normal mode) of carrying out theobservation under the observation condition set in view of the opticalparameters of the sample in the absence of the solid immersion lens, andthe second mode (solid immersion lens mode) of carrying out theobservation under the observation condition set in view of the opticalparameters of the sample and the solid immersion lens in the presence ofthe solid immersion lens. This makes it feasible to suitably acquire thenormal image/the enlarged image in the absence/in the presence of thesolid immersion lens, respectively, and thus to readily perform theobservation of the microstructure of the sample and the like.

Concerning the focusing for the sample, the microscope is preferablyconfigured so that the objective lens driving means comprises focusingmeans for changing a distance between the sample and the objective lensto carry out the focusing. Likewise, the sample observation method ispreferably configured so that in the correction step, the focusing iscarried out by changing a distance between the sample and the objectivelens.

Concerning the aberration correction, the microscope is preferablyconfigured so that the objective lens comprises a first lens unit and asecond lens unit arranged along the optical axis, and so that theobjective lens driving means comprises aberration correcting means forchanging a spacing between the first lens unit and the second lens unitto carry out the aberration correction. Similarly, the sampleobservation method is preferably configured so that in the correctionstep, the aberration correction is carried out by changing a spacingbetween a first lens unit and a second lens unit arranged along theoptical axis in the objective lens.

As a specific correction method, the microscope is preferably configuredso that the controlling means comprises a focusing table and anaberration correction table corresponding to the correction condition inthe solid immersion lens mode. Similarly, the sample observation methodis preferably configured so that the correction step is arranged to usea focusing table and an aberration correction table corresponding to thecorrection condition.

In the configuration that the switching of the observations in theabsence/in the presence of the solid immersion lens is carried out, themicroscope is preferably configured so that the controlling meanscomprises a focusing table (first focusing table) corresponding to thenormal correction condition (first correction condition) in the normalmode (first mode), and a focusing table (second focusing table) and anaberration correction table (second aberration correction table)corresponding to the correction condition (second correction condition)in the solid immersion lens mode (second mode). In this case, if theaberration correction in the normal mode is necessary, it is preferablethat the controlling means further comprises an aberration correctiontable (first aberration correction table) corresponding to thecorrection condition in the normal mode.

Similarly, the sample observation method is preferably configured sothat the normal correction step (first correction step) is arranged touse a focusing table (first focusing table) corresponding to the normalcorrection condition (first correction condition), and the correctionstep (second correction step) is arranged to use a focusing table(second focusing table) and an aberration correction table (secondaberration correction table) corresponding to the correction condition(second correction condition). In this case, if the aberrationcorrection in the normal correction step is necessary, it is preferablethat the normal correction step is further arranged to use an aberrationcorrection table (first aberration correction table) corresponding tothe correction condition.

By using the focusing tables and aberration correction tables in thismanner, it becomes feasible to readily and surely perform the focusingand aberration correction.

The microscope is preferably configured so that the solid immersion lensdriving means is a solid immersion lens moving device comprising: afirst arm member to which a solid immersion lens holder for supportingthe solid immersion lens is coupled; a first arm member rotation sourcefor rotating the first arm member in a horizontal plane substantiallyparallel to the sample; a second arm member for holding the first armmember rotation source; and a second arm member rotation source forrotating the second arm member in the horizontal plane and around arotational axis at a position not coaxial with a rotational axis of thefirst arm member rotation source.

Using this solid immersion lens moving device, the solid immersion lenscan be suitably moved between the insertion position and the standbyposition, relative to the sample, such as a semiconductor device, and tothe objective lens. In this case, further, the solid immersion lensmoving device preferably comprises a vertical movement source for movingthe second arm member rotation source in a vertical directionperpendicular to the horizontal plane.

Alternatively, as described later, the microscope is preferablyconfigured so that the microscope comprises a solid immersion lensholder including a base part to be attached to the objective lens, and alens holding part provided with the base part, extending in a directionof the optical axis of the objective lens, and holding the solidimmersion lens at an end portion thereof, wherein the lens holding partholds the solid immersion lens so that light emerging from the solidimmersion lens to the base part side travels through a region outsidethe lens holding part and toward the base part, and wherein the basepart has a light passing portion which transmits the light emerging fromthe solid immersion lens to the base part side, toward the objectivelens.

In this case, it is preferable that the lens holding part has: a holdingmember extending in the direction of the optical axis and receiving thesolid immersion lens; and a lens cover provided at an end portion of theholding member and having an opening for exposing a bottom surface ofthe solid immersion lens to the outside, wherein the lens holding parthouses the solid immersion lens between the holding member and the lenscover.

The microscope and sample observation method according to the presentinvention can be applied as a microscope and a sample observation methodcapable of readily observing a sample necessary for an analysis ofmicrostructure of a semiconductor device or the like. Namely, thepresent invention provides the microscope and sample observation methodcapable of readily performing the observation of microstructure of asample or the like, by carrying out the observation of the sample at thepredetermined observation plane and through the sample, by using thesolid immersion lens mode of carrying out the observation inconsideration of the optical parameters of the sample and solidimmersion lens with the solid immersion lens at the insertion positionincluding the optical axis from the sample to the objective lens.

Next, the solid immersion lens holder according to the present inventionwill be described below. Here, it should be noted that the solidimmersion lens holder described below can be suitably applied to theabove-described microscope and the sample observation method.

A solid immersion lens (SIL) is known as a lens for enlarging an imageof an observation object. This solid immersion lens is a lens of ahemispherical shape or a superhemispherical shape called a Weierstrasssphere, and microscopic lens in the size of about 1 mm-5 mm. When thissolid immersion lens is set in close contact with a surface of theobservation object, the numerical aperture (NA) and magnification bothare increased, so as to enable observation with a high spatialresolution.

One of the known techniques for securely keeping this solid immersionlens in close contact with the observation object is, for example, theone described in Document 1: U.S. Pat. No. 6,621,275. In thesemiconductor inspection system described in Document 1, the solidimmersion lens is mounted through a solid immersion lens holder in frontof an objective lens (i.e., on the observation object side). The solidimmersion lens holder has a chamber with a valve at an end portionthereof, and houses the solid immersion lens in the chamber. Thepressure inside the chamber is regulated through this valve to move thesolid immersion lens in the direction of the optical axis thereof toachieve optical coupling between the observation object and the solidimmersion lens.

The outer shape of this solid immersion lens holder is a tapered shapethe inner diameter of which decreases from the objective lens sidetoward the solid immersion lens side, and a light beam from the solidimmersion lens passes the interior of the solid immersion lens holder toenter the objective lens.

However, if the solid immersion lens is held by the solid immersion lensholder of the tapered shape with the solid immersion lens at the top asin the semiconductor inspection system described in Document 1, therewill arise a problem as described below, where an IC (semiconductordevice) as an observation object is housed in a socket or where a moldIC package having an IC molded with resin is inspected.

Namely, for example, in the case of an example in which an IC in a moldIC package (sample) is observed, the IC as a semiconductor device isburied in a plastic mold and, for observing the IC, the mold part isremoved to expose the back surface of the IC. In this case, the IC as anobservation object is located on a bottom surface of a recess. For thisreason, where the solid immersion lens holder is of the tapered shape,there can occur contact (interference) between the side wall of therecess and the outer peripheral surface of the solid immersion lensholder in the vicinity of the peripheral part of the IC. This results inposing a problem that the region near the peripheral part of the ICcannot be observed.

Therefore, an object of the present invention is to provide a solidimmersion lens holder permitting observation up to a region closer tothe peripheral part of the observation object even in the case where theobservation object is placed in a recess of a sample.

In order to solve the above problem, a solid immersion lens holderaccording to the present invention is a solid immersion lens holdercomprising: a base part to be attached to an objective lens; and a lensholding part provided with the base part, extending in a direction of anoptical axis of the objective lens, and holding a solid immersion lensat an end portion thereof, wherein the lens holding part holds the solidimmersion lens so that light emerging from the solid immersion lens tothe base part side travels through a region outside the lens holdingpart and toward the base part, and wherein the base part has a lightpassing portion which transmits the light emerging from the solidimmersion lens to the base part side, toward the objective lens.

In this case, the light passing portion is formed in the base part andthus the light beam from the solid immersion lens can be securely guidedinto the objective lens. For this reason, the observation object can beobserved even in a state in which the solid immersion lens is held bythe lens holding part. Since the solid immersion lens is held by thelens holding part extending in the direction of the optical axis of theobjective lens, for example, during observation of the observationobject located on a bottom surface of a recess, the lens holding part isprevented from coming into contact with the side wall of the recess evenif the solid immersion lens is moved to the vicinity of the peripheralpart of the observation object. As a result, it becomes feasible toobserve the peripheral part of the observation object.

In a preferred configuration of the above-described solid immersion lensholder, the lens holding part has: a holding member extending in thedirection of the optical axis and receiving the solid immersion lens;and a lens cover provided at an end portion of the holding member andhaving an opening for exposing a bottom surface of the solid immersionlens to the outside; the lens holding part houses the solid immersionlens between the holding member and the lens cover. The bottom surfaceof the solid immersion lens means a surface to be brought into contactwith the observation object.

In this configuration, the solid immersion lens is housed between a lensreceiver of the holding member, and the lens cover, whereby the solidimmersion lens is prevented from slipping off the lens holding part.

In the above-described solid immersion lens holder, preferably, theholding member has a plurality of lens receivers for receiving the solidimmersion lens. This permits the solid immersion lens to be held in astabler state. Since the solid immersion lens is received by theplurality of lens receivers, it is feasible to allow the light topropagate from the solid immersion lens to the base part side, betweenthe lens receivers.

In the above-described solid immersion lens holder, preferably, theplurality of lens receivers are radially arranged with respect to acenter line of the holding member. In this configuration, the pluralityof lens receivers are arranged apart in the circumferential direction,and thus partially receive the surface of the solid immersion lens onthe holding member side. For this reason, the light can be made tosecurely emerge from the solid immersion lens to the base part side evenin a state in which the solid immersion lens is received by the lensreceivers.

In a further preferred configuration, the plurality of lens receiversare arranged apart from each other with respect to the center line ofthe holding member. This enables the light even along the center line ofthe holding member to enter the objective lens, and it is thus feasibleto effectively use the light emerging from the solid immersion lens tothe base part side.

In the above-described solid immersion lens holder, preferably, the lensholding part has a clearance with respect to the solid immersion lens.This permits the solid immersion lens to follow the surface shape of theobservation object, and it results in bringing the solid immersion lensinto closer contact with the observation object.

Furthermore, the light passing portion of the above-described solidimmersion lens holder can be an aperture. In this case, preferably, anend of the lens holding part on the base part side is located in theaperture, and the base part has a connecting part for connecting thelens holding part to the base part. In this configuration, the lensholding part and the base part are securely coupled to each other by theconnecting part even if the lens holding part is located in theaperture.

The lens holding part of the above-described solid immersion lens holderis preferably provided integrally with the base part. In this case, itbecomes easy to produce the solid immersion lens holder.

Furthermore, the light passing portion of the above-described solidimmersion lens holder may have a light passing member.

In another configuration, the above-described solid immersion lensholder preferably further comprises a diaphragm provided in the basepart and arranged to limit a beam passing the light passing portion. Inthis case, the observation object can be observed through the use of abeam in a desired size. Since the diaphragm permits us, for example, tochange the size of the beam emerging from the objective lens andentering the solid immersion lens, it becomes feasible to regulate thenumerical aperture (NA) of the beam entering the observation object,and, as a result, it becomes feasible to observe the observation objectwith a desired NA.

Preferably, the above-described solid immersion lens holder isconfigured so as to protect the observation object to be observedthrough the solid immersion lens, in accordance with a stress exerted onthe solid immersion lens.

It is necessary to keep the solid immersion lens in close contact withthe observation object during observation of the observation objectthrough the solid immersion lens, but if the solid immersion lens ispressed against the observation object with too high pressure, theobservation object can be damaged. When the solid immersion lens ispressed against the observation object, the solid immersion lensreceives a reaction force, and it results in exerting a stress on thelens holding part holding the solid immersion lens. For this reason, byprotecting the observation object in accordance with the stress exertedon the lens holding part, it is feasible to observe the observationobject through the use of the solid immersion lens held by the solidimmersion lens holder, without damage to the observation object.

In a further preferred configuration, the above-described solidimmersion lens holder further comprises a stress detection sensor fordetecting a stress exerted on the solid immersion lens.

In this case, the stress detection sensor detects the stress exerted onthe lens holding part, and it is thus feasible to keep the solidimmersion lens in close contact with the observation object, withoutdamage to the observation object.

Another solid immersion lens holder according to the present inventionis a solid immersion lens holder for holding a solid immersion lens tobe used in observation of an observation object placed in a recess of asample, the solid immersion lens holder being attached to an objectivelens, holding the solid immersion lens so as to avoid contact with aside wall of the recess during observation of a peripheral part of theobservation object, and transmitting light emerging from the solidimmersion lens to the objective lens side, toward the objective lens.

Since this configuration permits the light emerging from the solidimmersion lens to the objective lens side to be transmitted while thesolid immersion lens holder holds the solid immersion lens, it isfeasible to observe the observation object. Since the solid immersionlens holder holds the solid immersion lens so as to avoid contact withthe side wall of the recess during the observation of the peripheralpart of the observation object, it is feasible to securely observe theperipheral part of the observation object located in the recess.

The solid immersion lens holder according to the present inventionpermits us to observe a region closer to the peripheral edge of theobservation object even in the case where the observation object islocated inside the recess.

The preferred embodiments of the solid immersion lens holder accordingto the present invention will be described below with reference to thedrawings. The same elements will be denoted by the same referencesymbols in each of drawings, without redundant description.

First Embodiment

FIG. 21 is a configuration diagram showing a semiconductor inspectionapparatus provided with the solid immersion lens holder according to thefirst embodiment of the present invention. FIG. 22 is a configurationdiagram showing a configuration of the solid immersion lens holder. FIG.23 is an exploded perspective view of the solid immersion lens holder.FIG. 24(a) is a sectional view along line IV-IV in FIG. 23, and FIG.24(b) an enlarged view of an end portion of a lens holding part in thesolid immersion lens holder shown in FIG. 24(a). FIG. 22 shows a statein observation of a sample while the solid immersion lens holder ismounted on an objective lens. FIGS. 23, 24(a), and 24(b) show a state inwhich the solid immersion lens holder holds a solid immersion lens. FIG.24(b) shows a state in which the solid immersion lens is pressed againstan observation object.

As shown in FIGS. 21 and 22, the semiconductor inspection apparatus 201is, for example, a inspection device that inspects as an observationobject a semiconductor device 211 (cf. FIG. 22) in a mold semiconductordevice being a sample 210 and that is arranged to acquire an image ofthe semiconductor device 211 and to inspect internal informationthereof.

The “mold semiconductor device” is a device in which the semiconductordevice 211 is hermetically sealed as molded with resin 212. The“internal information” includes a circuit pattern of the semiconductordevice and very weak emission from the semiconductor device. Examples ofthis very weak emission include emission from an abnormal part based ona defect of the semiconductor device, transient emission with aswitching operation of a transistor in the semiconductor device, and soon. Furthermore, the very weak emission also includes heat generatedbased on a defect of the semiconductor device.

The sample 210 is mounted on a stage 202 in an observation part A andwith the back surface of the semiconductor device 211 facing up, in astate in which the resin 212 is cut away so as to expose the backsurface of the semiconductor device 211 buried in the resin 212. Sincethe back surface of the semiconductor device 211 is exposed by cuttingthe sample 210 in part away in this manner, the semiconductor device 211is located on a bottom surface of recess 213 resulting from the cuttingof the resin 212. Then the inspection apparatus 201, in the presentembodiment, inspects the illustrated lower surface of the semiconductordevice 211 (an integrated circuit formed on a front surface of asubstrate of semiconductor device 211, or the like).

The semiconductor inspection apparatus 201 is provided with anobservation part A for observation of semiconductor device 211, acontrol part B for control on operations of respective parts in theobservation part A, and an analysis part C for processing, instructions,etc. necessary for inspection of semiconductor device 211.

The observation part A is provided with a high-sensitivity camera 203and a laser scan optic (LSM: Laser Scanning Microscope) unit 204 asimage acquiring means for acquiring an image from the semiconductordevice 211, an optical system 220 including objective lens 221 ofmicroscope 205 disposed between the high-sensitivity camera 203 and LSMunit 204, and the semiconductor device 211, a solid immersion lens 206(cf. FIG. 22) for acquiring an enlarged observation image ofsemiconductor device 211, and an XYZ stage 207 for moving these memberseach in X-Y-Z directions orthogonal to each other.

The optical system 220 is provided with an optical system 222 for thecamera and an optical system 223 for the LSM unit, in addition toobjective lens 221. There are a plurality of objective lenses 221 withdifferent magnifications provided so as to be switchable. The objectivelens 221 has a correction ring 224 to permit an observer to adjust thecorrection ring 224 so as to securely achieve focus on a locationdesired to observe. The camera optical system 222 guides light from thesemiconductor device 211 through the objective lens 221, to thehigh-sensitivity camera 203, and the high-sensitivity camera 203acquires an image of a circuit pattern or the like of the semiconductordevice 211.

On the other hand, the LSM unit optical system 223 reflects an infraredlaser beam from the LSM unit 204 toward the objective lens 221 by a beamsplitter (not shown) to guide the beam to the semiconductor device 211,and guides the reflected laser beam traveling from the semiconductordevice 211 toward the high-sensitivity camera 203 through the objectivelens 221, to the LSM unit 204.

This LSM unit 204 emits the infrared laser beam toward the semiconductordevice 211 while scanning it in the X-Y directions, and detects thereflected light from the semiconductor device 211 by a photodetector(not shown). The intensity of this detected light is one reflecting thecircuit pattern of the semiconductor device 211. Therefore, the LSM unit204 acquires an image of the circuit pattern of the semiconductor device211 or the like by the X-Y scan on the semiconductor device 211 with theinfrared laser beam.

The XYZ stage 207 is a mechanism for moving the high-sensitivity camera203, LSM unit 204, optical system 220, solid immersion lens 206, etc. ineach of the X-Y directions (horizontal directions; directions parallelto the semiconductor device 211 as an observation object) and theZ-direction (vertical direction) orthogonal to them, according to need.

As shown in FIG. 22, the solid immersion lens 206 is a microscopic lensof hemispherical shape and has a hemispherical part 206 b having anupper surface 206 a being an input/output surface for light to theoutside (e.g., the objective lens of the microscope) and formed in thespherical shape. The solid immersion lens 206 has a convex part 206 dthat is protruded in the opposite direction to the upper surface 206 aside and in the central region of the solid immersion lens 206 and thathas a bottom surface 206 c formed in planar shape. This bottom surface206 c is a mount surface onto the semiconductor device 211. The solidimmersion lens 206 is arranged so that the bottom surface 206 c isbrought into close contact with an observation position (on theillustrated upper surface) for observation to acquire an enlargedobservation image of the front surface (illustrated lower surface) ofthe semiconductor device 211 being the back side. Specifically, thesolid immersion lens used in the semiconductor inspection apparatus ismade of a high-index material having a refractive index substantiallyequal to or close to the refractive index of the substrate material ofthe semiconductor device. Typical examples of the material include Si,GaP, GaAs, and so on.

The microscopic optical element as described above is kept in opticallyclose contact with the surface of the substrate of the semiconductordevice, whereby the semiconductor substrate itself is used as a part ofthe solid immersion lens. In a back surface analysis of thesemiconductor device with the solid immersion lens, when the focus ofthe objective lens is matched with the integrated circuit formed on thefront surface of the semiconductor substrate, the effect of the solidimmersion lens enables a beam with a high NA to pass in the substrate,and the apparatus is expected to achieve a high resolution.

The lens shape of the solid immersion lens 206 as described above isdetermined depending upon conditions for elimination of aberration. Inthe case of the solid immersion lens 206 having the hemispherical shape,the focus thereof is at the center of the sphere. In this case, thenumerical aperture (NA) and magnification both are multiplied by n. Theshape of the solid immersion lens 206 does not have to be limited to thehemispherical shape, but may be, for example, the Weierstrass shape.

The solid immersion lens holder 208A is one suitably holding the solidimmersion lens 206 relative to the objective lens 221 and is attachedthrough an objective lens socket 209 to the objective lens 221. Thissolid immersion lens holder 208A will be described later in detail. Theobjective lens socket 209 is provided at the end portion of theobjective lens 221 and is used for mounting the solid immersion lensholder 208A on the objective lens 221. In a state in which the solidimmersion lens holder 208A is mounted on the objective lens 221, theobjective lens socket 209 is arranged to pass light inside thereof so asto permit observation of the semiconductor device 211.

The control part B is provided with a camera controller 231, a laserscan (LSM) controller 232, and a peripheral controller 233. The cameracontroller 231 and LSM controller 232 control respective operations ofthe high-sensitivity camera 203 and the LSM unit 204, therebycontrolling execution of observation of the semiconductor device 211(acquisition of an image), setting of observation conditions, etc.performed in the observation part A.

The peripheral controller 233 controls the operation of the XYZ stage207, thereby controlling movement, positioning, focusing, etc. of thehigh-sensitivity camera 203, LSM unit 204, optical system 220, etc. topositions corresponding to the observation position of the semiconductordevice 211. In addition, the peripheral controller 233 drives a motor225 for adjustment of the correction ring attached to the objective lens221, so as to adjust the correction ring 224.

The analysis part C is provided with an image analyzer 241 and aninstructor 242 and is constructed of a computer. The image analyzer 241executes analysis processes and others necessary for image informationfrom the camera controller 231 and from the LSM controller 232, and theinstructor 242 refers to an entry entered by an operator, analysiscontents by the image analyzer 241, etc. to give necessary instructionsabout execution of inspection of the semiconductor device 211 in theobservation part A, through the control part B. An image, data, or thelike acquired or analyzed by the analysis part C is displayed on adisplay unit 243 connected to the analysis part C, according to need.

Next, the solid immersion lens holder 208A, which is the feature of thepresent embodiment, will be detailed in particular. In the descriptionbelow, the side of objective lens 221 relative to the solid immersionlens 206 will be referred to as the upper side and the side of sample210 as the lower side, for simplification of description.

As shown in FIGS. 23 and 24, the solid immersion lens holder 208A isconstructed so that a lens holding part 260 extends from a center of abase part 250 of disk shape and in a direction substantiallyperpendicular to the base part 250, and the outer shape thereof is ofsubstantially T-shape, when viewed from a direction of arrow A1 in FIG.23.

The base part 250 has a peripheral wall 251 for screwing with theobjective lens socket 209 (cf. FIG. 22) and the base part 250 is engagedwith the objective lens socket 209 to mount the solid immersion lensholder 208A so that the center of the base part 250 is located on theoptical axis L of the objective lens 221. This results in permitting theposition of the solid immersion lens 206 held by the solid immersionlens holder 208A to be adjusted through driving of the XYZ stage 207.The outer surface of the peripheral wall 251 is knurled so as tofacilitate mounting of the base part 250 on the objective lens socket209.

A bottom plate 252 of the base part 250 has three apertures 253, 253,253 as light passing portions for letting a light beam pass. Eachaperture 253 passes the light from the LSM unit 204 toward the solidimmersion lens 206 and passes the light reflected by the semiconductordevice 211 and emerging from the solid immersion lens 206, toward theobjective lens 221.

Each aperture 253 is approximately sector-shaped and the apertures 253are arranged concentrically with each other with respect to the centerof the base part 250 and at equal intervals in the circumferentialdirection. This results in forming three connecting parts 254, 254, 254for connecting the lens holding part 260 to the bottom plate 252, atequal intervals between adjacent apertures 253, 253. In other words, thebase part 250 has the connecting parts 254, 254, 254 traversing acircular aperture formed concentrically with the center of the bottomplate 252 and connecting the bottom plate 252 to the lens holding part260. The three connecting parts 254, 254, 254 radially extend from thecenter of the base part 250.

The lens holding part 260 has a holding member 261 extending from theintersecting part among the connecting parts 254, 254, 254 and in adirection substantially perpendicular to the base part 250. The holdingmember 261 is comprised of three holding pieces 262, 262, 262 located onthe respective connecting parts 254, 254, 254 and serving as lensreceivers for receiving the solid immersion lens 206.

The holding pieces 262, 262, 262 are radially arranged with respect tothe center line of the holding member 261 (more specifically, in theY-shape) and each holding piece 262 has a tapered shape the width d ofwhich decreases toward the center line of the holding member 261 (inother words, toward the inside). This can achieve more reduction in thequantity of light blocked by the holding piece 262 among the lightentering or leaving the upper surface 206 a of the solid immersion lens206. The length of the holding piece 262 in the direction of the opticalaxis L is longer than the depth of the recess 213 of the sample 210 (thelength in the direction of the optical axis L). This permits theapparatus to observe the semiconductor device 211 located on the lowersurface of the recess 213 of the sample 210, in a state in which thesolid immersion lens holder 208A holds the solid immersion lens 206.

The holding pieces 262, 262, 262 and the base part 250 are integrallyformed, for example, with a resin so that the center line of the holdingmember 261 passes the center of the base part 250. This matches theoptical axis L of the objective lens 221 with the center line of theholding member 261. For this reason, the center line of the holdingmember 261 will also be denoted by symbol L in the descriptionhereinafter.

The holding pieces 262, 262, 262 have their respective lens receivingsurfaces 262 a, 262 a, 262 a formed at the end portion thereof (i.e., atthe end on the opposite side to the base part 250) and having acurvature equal to that of the upper surface 206 a of the solidimmersion lens 206, and the holding member 261 receives the solidimmersion lens 206 by the three lens receiving surfaces 262 a. Thispermits the holding member 261 to stably receive the solid immersionlens 206. In addition, a claw 262 b for fixing a lens cover 263 ofcylindrical shape is formed at the end portion of each holding piece262, 262, 262.

The lens cover 263 has a bottom plate 264, and the peripheral part ofthe bottom plate 264 is provided with a peripheral wall 265 to beengaged with the claws 262 b. The inner diameter of the peripheral wall265 is larger than the outer diameter of the solid immersion lens 206.The bottom plate 264 has an opening 264 a for letting the bottom surface206 c of the solid immersion lens 206 project to the outside (toward thesample 210), and the diameter of this opening 264 a (cf. FIG. 24(b)) islarger than the outer diameter of the bottom surface 206 c part in thesolid immersion lens 206.

In this configuration, after the solid immersion lens 206 is placedbetween the lens receiving surfaces 262 a and the lens cover 263, thelens cover 263 is fixed to the holding member 261 with an adhesive orthe like, whereby the solid immersion lens 206 is housed in a state inwhich the bottom surface 206 c projects out of the opening 264 a,between the lens receiving surfaces 262 a and the lens cover 263. Thisprevents the solid immersion lens 206 from slipping off the lens holdingpart 260.

In a state in which the lens cover 263 is fixed to the holding member261, the space for housing of the solid immersion lens 206 created bythe bottom plate 264 and the three lens receiving surfaces 262 a islarger than the hemispherical part 206 b of the solid immersion lens206. Therefore, the lens holding part 260 has a play relative to thesolid immersion lens 206 and, in other words, has a clearance (space).

For this reason, during observation of the semiconductor device 211, thesolid immersion lens 206 can swing so that the solid immersion lens 206follows the surface shape of the semiconductor device 211; for example,the semiconductor device 211 can be observed even in a case where thesemiconductor device 211 is inclined relative to the optical axis L.Furthermore, the degree of close contact is improved between the solidimmersion lens 206 and the semiconductor device 211. In addition, evenif the solid immersion lens 206 swings in this manner, the position ofobservation with the solid immersion lens 206 agrees with the center ofthe sphere, so as not to affect the observation.

The following will describe an example of a method of acquiring an imageof the semiconductor device 211 with the semiconductor inspectionapparatus 201.

First, a position for observation of the semiconductor device 211 withthe solid immersion lens 206 is specified using an objective lens 221without the solid immersion lens 206, out of the plurality of objectivelenses 221 in the microscope 205. This operation of specifying theobservation position is carried out by driving the XYZ stage 207 throughthe peripheral controller 233 by the instructor 242.

After the specifying operation of the observation position, theobjective lens is switched to an objective lens 221 with the solidimmersion lens holder 208A and observation is carried out therewith. Onthis occasion, the instructor 242 adjusts the correction ring 224 to anappropriate position by driving the correction ring adjustment motor 225through the peripheral controller 233 in accordance with thecharacteristics of the solid immersion lens 206 held by the solidimmersion lens holder 208A (the thickness of the solid immersion lens206, the refractive index thereof, etc.), the thickness of the substrateof the semiconductor device 211, the material of the substrate, and soon.

The instructor 242 drives the XYZ stage 207 through the peripheralcontroller 233 in accordance with the characteristics of the solidimmersion lens 206 and others to press the solid immersion lens 206against the semiconductor device 211 to achieve close contact. Theinstructor 242 also drives the XYZ stage 207 through the peripheralcontroller 233 to bring the objective lens 221 in focus. When the solidimmersion lens 206 is in close contact with the semiconductor device 211in this manner, the solid immersion lens 206 is pushed toward the lensreceiving surface 262 a side by the semiconductor device 211, and thusthe upper surface 206 a comes into contact with the lens receivingsurfaces 262 a (cf. FIG. 24(b)).

In the in-focus state of the objective lens 221, the instructor 242 thenexecutes observation of the semiconductor device 211 by use of the LSMunit 204, high-sensitivity camera 203, etc. through the LSM controller232 and the camera controller 231.

In this observation, the infrared laser beam outputted from the LSM unit204 is outputted through the objective lens 221 and toward the sample210. The light outputted from the objective lens 221 passes through theapertures 253 of the base part 250, enters the solid immersion lens 206from the upper surface 206 a thereof, and is outputted toward thesemiconductor device 211. Then light (reflected light) reflected fromthe semiconductor device 211 under irradiation with the infrared laserbeam is again incident to the solid immersion lens 206 and is outputtedfrom the upper surface 206 a of the solid immersion lens 206. Morespecifically, the reflected light from the semiconductor device 211 isoutputted from the portions of the upper surface 206 a not contactingthe lens receiving surfaces 262 a.

The reflected light emerging from this solid immersion lens 206propagates through a region outside the lens holding part 260 (includingthe space between adjacent holding pieces 262) toward the base part 250.Then the light travels through the apertures 253 of the base part 250 toenter the objective lens 221. The reflected light entering the objectivelens 221 is guided to the high-sensitivity camera 203 by the cameraoptical system 222, and the high-sensitivity camera 203 acquires animage of the circuit pattern of the semiconductor device 211 or thelike. In this semiconductor inspection apparatus 201, the solidimmersion lens 206 can be replaced by changing the solid immersion lensholder 208A with another. In this case, the lens replacement is easybecause there is no need for directly handling the small solid immersionlens 206.

Since the whole solid immersion lens holder 208A is changed with anotherduring the lens replacement as described above, it is preferable to forma notch or the like as a mark for discriminating the solid immersionlens 206 held by the lens holding part 260, in the holding pieces 262 ofthe holding member 261. This permits the operator to readily know thecharacteristics of the solid immersion lens 206 (refractive index,thickness, etc.) held by the solid immersion lens holder 208A, by only alook at the solid immersion lens holder 208A. Other marks fordiscriminating the solid immersion lens 206 can be, for example,different colors for the lens holding part 260.

For inspecting the semiconductor device 211 of the sample 210 with useof the semiconductor inspection apparatus 201, as described above, it isimportant for the lens holding part 260 of the solid immersion lensholder 208A to extend in the direction of the optical axis L of theobjective lens 221 (in the direction approximately perpendicular to thebase part 250) and for the solid immersion lens holder 208A to have theapproximately T-shape.

Namely, since the lens holding part 260 extends in the direction of theoptical axis L of the objective lens 221, the lens holding part 260 isapproximately parallel to the side wall 213 a of the recess 213 (cf.FIG. 22). For this reason, the lens holding part 260 is unlikely tointerfere (in other words, contact) with the side wall 213 a of therecess 213 even if the solid immersion lens 206 is moved to near theperipheral part of the semiconductor device 211 provided on the lowersurface of the recess 213. As a result, the observation can be conductedwhile the solid immersion lens 206 is located closer to the peripheralpart 211 a of the semiconductor device 211 positioned in the recess 213.In order to allow the lens holding part 260 to be located closer to thevicinity of the side wall 213 a of the recess 213, the outside diameterof the lens holding part 260 is preferably slightly larger than theoutside diameter of the solid immersion lens 206.

In the solid immersion lens holder 208A, since the upper surface 206 aof the solid immersion lens 206 is partly received by the three holdingpieces 262 radially arranged with respect to the center line L of theholding member 261, light can be securely inputted or outputted from theportions out of contact with the holding pieces 262 in the upper surface206 a of the solid immersion lens 206 even if the lens holding part 260extending in the direction of the optical axis L holds the solidimmersion lens 206.

Since the base part 250 has the apertures 253, the light (infrared laserbeam) from the LSM unit 204 can be guided well into the solid immersionlens 206 and the light from the solid immersion lens 206 can also beguided well into the objective lens 221 even if the solid immersion lensholder 208A is mounted on the objective lens 221.

Furthermore, since the solid immersion lens holder 208A is mounted onthe objective lens 221, the position of the solid immersion lens 206 canbe adjusted by moving the objective lens 221 by the XYZ stage 207. Forobserving the semiconductor device 211, the objective lens 221 is movedin the direction of the optical axis L of the objective lens 221,whereby the solid immersion lens 206 is brought into close contact withthe semiconductor device 211. Therefore, for example, even in a casewhere the solid immersion lens holder 208A is applied to an invertedmicroscope, as well as the erecting microscope 205 as shown in FIG. 21,the solid immersion lens 206 can be securely kept in close contact withthe semiconductor device 211.

Second Embodiment

FIG. 25 is a bottom view of solid immersion lens holder 208B accordingto the second embodiment. FIG. 25 shows a state in which the solidimmersion lens holder 208B holds a solid immersion lens 206.

The configuration of the solid immersion lens holder 208B is differentfrom the configuration of the solid immersion lens holder 208A shown inFIG. 23, in that the width of connecting parts 281, 281, 281 is narrowedin part in the extending direction of each connecting part 281 (i.e., inthe radial directions of the base part 250). The solid immersion lensholder 208B will be described with focus on this point.

Since the width of the connecting parts 281 is narrowed in part, theconnecting parts 281 will be broken if a predetermined stress is exertedthrough the solid immersion lens 206 or the like on the holding member261.

Since the solid immersion lens 206 has to be brought into close contactwith the semiconductor device 211 in order to observe the semiconductordevice 211 through the solid immersion lens 206, the solid immersionlens 206 is pressed against the semiconductor device 211. In this case,for example, if the solid immersion lens 206 is pushed too hard, thesemiconductor device 211 might be damaged. This is also the case in theoperation of moving the solid immersion lens 206 for scan on thesemiconductor device 211.

In contrast to it, the width of the connecting parts 281 is narrowed inpart in the configuration of the solid immersion lens holder 208B, andwhen the solid immersion lens 206 is pushed against the semiconductordevice 211, the connecting parts 281, 281, 281 break before damage tothe semiconductor device 211, so as to result in first breaking thesolid immersion lens holder 208B.

Describing it in more detail, when the solid immersion lens 206 ispressed against the semiconductor device 211, the solid immersion lens206 receives a force as reaction from the semiconductor device 211. As aresult, a stress is exerted on the holding member 261 in contact withthe upper surface 206 a of the solid immersion lens 206, whereupon thestress is applied to the connecting parts 281 provided integrally withthe holding member 261. The connecting parts 281 break when the stressexceeds a predetermined value. For this reason, the semiconductor device211 is prevented from receiving a load over a certain level duringinspection of the semiconductor device 211, whereby the semiconductordevice 211 is prevented from being damaged.

Namely, the solid immersion lens holder 208B has the configuration forprotecting the semiconductor device 211 as an observation object inaccordance with the stress exerted on the lens holding part 260 duringobservation, based on the width of the connecting parts 281 narrowed inpart. The width of the narrowed portions in the connecting parts 281 canbe determined so that the connecting parts 281 can break before damageto the semiconductor device 211 in accordance with the stress exerted onthe connecting parts 281.

The effect of the configuration wherein the holding member 261 extendsin the direction of the optical axis L of the objective lens 221 is muchthe same as in the case of the first embodiment. Namely, since the lensholding part 260 is unlikely to contact the side wall 213 a of therecess 213 (cf. FIG. 22), it becomes feasible to move the lens holdingpart 260 up to the vicinity of the side wall 213 a of recess 213. As aresult, the peripheral part 211 a of the semiconductor device 211 can beobserved.

The present embodiment adopted the configuration wherein the width ofthe connecting parts 281 was narrowed, but it is also possible to adopt,for example, a configuration wherein the thickness of connecting parts281 (the length in the direction perpendicular to the bottom plate 252)is decreased in part.

Third Embodiment

FIG. 26 is a bottom view of solid immersion lens holder 208C accordingto the third embodiment. FIG. 26 shows a state in which the solidimmersion lens holder 208C holds a solid immersion lens 206.

The configuration of the solid immersion lens holder 208C is differentfrom the configuration of the solid immersion lens holder 208A shown inFIG. 23, in that the solid immersion lens holder 208C has three stressdetection sensors S, S, S. The solid immersion lens holder 208C will bedescribed with focus on this point.

A stress detection sensor S is stuck onto each connecting part 254 anddetects the stress exerted through the lens holding part 260 on theconnecting part 254 during observation of the semiconductor device 211,as described in the second embodiment. The stress detection sensors Scan be, for example, strain gages.

The stress detection sensors S are electrically connected through theperipheral controller 233 to the instructor 242 (cf. FIG. 21), and theinstructor 242 terminates the inspection with the semiconductorinspection apparatus 201 when the stress detected by the stressdetection sensors S exceeds a predetermined stress. More specifically,the instructor 242 suspends the operation of the XYZ stage 207 by theperipheral controller 233 to terminate the adjustment of the observationposition, focusing, and so on.

This can suspend such operations as position adjustment of the solidimmersion lens 206 before damage to the semiconductor device 211 due topushing of the solid immersion lens 206 or the like, whereby thesemiconductor device 211 can be protected, as in the case of the secondembodiment. Namely, the solid immersion lens holder 208C has theconfiguration for protecting the semiconductor device 211 as anobservation object, thanks to the possession of the stress detectionsensors S.

The effect of the configuration wherein the lens holding part 260extends in the direction of the optical axis L of the objective lens 221is much the same as in the case of the first embodiment. There are noparticular restrictions on the setting locations of the stress detectionsensors S as long as they can detect the stress exerted on the lensholding part 260.

Fourth Embodiment

FIG. 27 is an exploded side view of solid immersion lens holder 208Daccording to the fourth embodiment. FIG. 27 shows a state in which thesolid immersion lens holder 208D holds a solid immersion lens 206.

The configuration of solid immersion lens holder 208D is mainlydifferent from the configuration of the solid immersion lens holder 208Ashown in FIG. 23, in that the lens holding part 290 is detachablyattached through the bottom plate 252 of the base part 100 to the basepart 100. The solid immersion lens holder 208D will be described withfocus on this point.

The holding member 291 forming the lens holding part 290 has aprojection 292 on the bottom plate 252 side of the base part 100. Thebottom plate 252 has a boss 101 to engage with the projection 292, atthe intersection among the three connecting parts 254, 254, 254 (cf.FIG. 23). In the solid immersion lens holder 208D, therefore, the lensholding part 290 can be connected to the base part 100 throughengagement of the projection 292 with the boss 101.

In this configuration the lens holding part 290 can be attached to anddetached from the base part 100, whereby the solid immersion lens 206can be readily changed in a state in which the base part 100 is mountedthrough the objective lens socket 209 on the objective lens 221.

The holding member 291 extends in the direction of the optical axis L asthe holding member 261 shown in FIG. 23 does, and the effect of theconfiguration wherein the holding member 291 extends in the direction ofthe optical axis L is much the same as in the case of the firstembodiment; it is feasible to observe the object up to a region closerto the peripheral part 211 a of the semiconductor device 211.

Fifth Embodiment

FIG. 28 is a bottom view of solid immersion lens holder 208E accordingto the fifth embodiment. FIG. 29 is a sectional view along line IX-IX inFIG. 28. FIGS. 28 and 29 show a state in which the solid immersion lensholder 208E holds a solid immersion lens 206.

The configuration of the solid immersion lens holder 208E is differentfrom the configuration of the solid immersion lens holder 208A shown inFIG. 23, in that the solid immersion lens holder 208E has a diaphragm110 for limiting a light beam passing the base part 250. The solidimmersion lens holder 208E will be described with focus on this point.

The outer shape of the diaphragm 110 is of a disk shape and is attachedto the base part 250 by engaging three hooks 111, 111, 111 ofapproximately L-shape provided on the bottom surface of the diaphragm110 (the surface on the base part 250 side), with correspondingconnecting parts 254, 254, 254. The diaphragm 110 is arrangedconcentrically with the center of the base part 250 and is located onthe upper surface side of the bottom plate 252. The diaphragm 110restricts the beam passing through the apertures 253 of the base part250, by a circular aperture 112 formed in the central region thereof.

Since the diaphragm 110 is attached to the base part 250 by engaging thehooks 11.1 with the connecting parts 254 as described above, it isattachable to and detachable from the base part 250. For this reason, bypreparing a plurality of diaphragms 110 with different sizes of aperture112, it is feasible to adjust the size of the beam passing the base part250. By adjusting the size of the aperture 112 of the diaphragm 110 inthis manner, the NA of the beam incident to the semiconductor device 211can be varied, so that the semiconductor device 211 can be observed withany desired NA.

In the semiconductor device, for example, where a plurality of layerswith different refractive indices are stacked between the surface incontact with the solid immersion lens 206 and the observation positionthrough the solid immersion lens 206, total reflection can occur betweenlayers, depending upon the NA of the beam incident to the semiconductordevice, and the light can fail to adequately arrive at the desiredobservation position. In addition, the totally reflected light can passthrough the solid immersion lens 206 and objective lens 221 to enter thehigh-sensitivity camera 203, so as to degrade the image.

In contrast to it, the present embodiment is configured to adjust the NAof the beam incident to the semiconductor device 211 by the diaphragm110 as described above, whereby the light can securely arrive at thedesired observation position, without occurrence of total reflectionbetween layers. In this case, the totally reflected light between layersis prevented from again entering the objective lens 221 through thesolid immersion lens 206, whereby the semiconductor device 211 can beobserved as a sharper image. It is also possible to provide a liquidcrystal diaphragm instead of the diaphragm 110.

The effect of the configuration wherein the lens holding part 260extends in the direction of the optical axis L is much the same as inthe case of the first embodiment, and it is feasible to observe theobject up to a region closer to the peripheral part 211 a of thesemiconductor device 211.

Sixth Embodiment

FIG. 30 is an exploded perspective view of solid immersion lens holder208F according to the sixth embodiment. FIG. 30 shows a case in whichthe solid immersion lens holder 208F holds a solid immersion lens 206.

The configuration of the solid immersion lens holder 208F is mainlydifferent from the configuration of the solid immersion lens holder 208Ashown in FIG. 23, in that three holding pieces 121, 121, 121 of holdingmember 120 are arranged apart from the center line L of the holdingmember 120. The solid immersion lens holder 208F will be described withfocus on this point.

Each holding piece 121 is radially arranged with respect to the centerline L of the holding member 120 passing the center of the base part 130and is located an equal distance apart from the center line L. Eachholding piece 121 extends from an end of each connecting part 131 and ina direction substantially perpendicular to the base part 130 (i.e., inthe direction of the optical axis L). The holding pieces 121 adjacent toeach other are coupled by a connecting member 122 of arcuate shapeintegrally formed with the holding pieces 121. For this reason, thepositional relation among three holding pieces 121, 121, 121 is securelyfixed. Each holding piece 121 has a lens receiving surface 262 a and aclaw 262 b at the end portion thereof as the holding piece 262 shown inFIG. 23 did.

In this configuration, the three holding pieces 121 are not connected onthe center line L and the connecting parts 131 do not intersect at thecenter of the bottom plate 252 (the center of the base part 130) in thebase part 130, either. For this reason, the three apertures 253 shown inFIG. 23 are communicated with each other at the center of the bottomplate 252 (the center of the base part 130) to form one aperture. Inother words, the solid immersion lens holder 208F has a circularaperture 132 formed as centered on the center of the bottom plate 252,and is configured so that the bottom plate 252 is coupled to the ends ofthe holding pieces 121 located in the aperture 132, by the connectingparts 131 extending from the peripheral part of the aperture 132 towardthe center and shorter than the radius of the aperture 132.

In the solid immersion lens holder 208F having the configuration asdescribed above, the light entering and leaving the upper surface 206 aof the solid immersion lens 206 is further prevented from being blockedby the holding pieces 121, whereby the light beam can be effectivelyutilized. Since the light can pass the center and surroundings of thebase part 130 and through the interior of the holding member 120, moreimage information can be acquired from the semiconductor device 211.

Since the light is also allowed to pass the region near the center lineL of the lens holding part 260 in the solid immersion lens holder 208Fas described above, it is preferable to adopt the configuration whereinthe holding pieces 121 are formed so that the distance from the centerline L to each holding piece 121 decreases from the base part 130 sidetoward the solid immersion lens 206 side, as shown in FIG. 30, in termsof effective utilization of the beam.

The present embodiment adopted the configuration wherein the holdingpieces 121 adjacent to each other were coupled by the connecting member122, but it is also possible to adopt a configuration without theconnecting member 122, because the holding pieces 121 adjacent to eachother are also coupled by the lens cover 263 fixed to the claws 262 bformed in the holding pieces 121.

The effect of the configuration wherein the lens holding part 260 havingthe holding member 120 and lens cover 263 extends in the direction ofthe optical axis L is much the same as in the case of the firstembodiment, and it is feasible to observe the object up to a regioncloser to the peripheral part 211 a of the semiconductor device 211.

Seventh Embodiment

FIG. 31 is a view of solid immersion lens holder 208G according to theseventh embodiment, from the side of objective lens 221. FIG. 32 is asectional view along line XII-XII in FIG. 31. FIG. 33 is a view of thesolid immersion lens holder 208G from a direction of arrow A2 in FIG.32. FIGS. 31 to 33 show a state in which the solid immersion lens holder208G holds a solid immersion lens 206.

The configuration of the solid immersion lens holder 208G is mainlydifferent from the configuration of the solid immersion lens holder 208Ashown in FIG. 23, in that the light passing portion 140 of the solidimmersion lens holder 208G has a glass plate 141 as a light passingmember. The solid immersion lens holder 208G will be described withfocus on this point.

The light passing portion 140 is comprised of a circular aperture 142formed concentrically with the center of the base part 250, and a glassplate 141 provided on the upper surface of the base part 250. The glassplate 141 has a glass plate body 143 of disk shape, and mount pieces 144projecting in radial directions from the peripheral part of the glassplate body 143. The diameter of the glass plate body 143 of the glassplate 141 is larger than the diameter of the aperture 142. For thisreason, when the glass plate 141 is placed so as to cover the aperture142, the mount pieces 144 are located on the bottom plate 252 of thebase part 250.

The glass plate 141 is fixed through the mount pieces 144 so that thecenter of the base part 250 is located on the center line L of theholding member 151. The width of the mount pieces 144 is narrowed inconnecting part to the glass plate body 143.

A mount portion 160 of cylindrical shape to engage with a projection 152of the holding member 151 of the lens holding part 150 is buried in thecenter of the glass plate 141. By engaging this mount portion 160 withthe projection 152, the lens holding part 150 is attached to the glassplate 141. The relation of the mount portion 160 with the holding member151 having the projection 152 is similar to the relation of the boss 101with the holding member 291 of the solid immersion lens holder 208D inthe fourth embodiment.

In the configuration of this solid immersion lens holder 208G the basepart 250 and the lens holding part 150 are attachable to and detachablefrom each other, and thus the solid immersion lens 206 can be readilyreplaced with another even in a state in which the base part 250 isfixed to the objective lens 221.

Since the width of the mount pieces 144 is narrowed on the glass platebody 143 side, the glass plate 141 will break before damage to thesemiconductor device 211 during position adjustment of the solidimmersion lens 206, focusing, or the like, for the same reason as in thecase of the solid immersion lens holder 208D shown in FIG. 25. As aresult, the semiconductor device 211 is protected.

Furthermore, the aperture 142 can pass the beam in the region except forthe mount portion 160 in the base part 250, whereby the blocking of thebeam from the solid immersion lens 206 is further suppressed. As aresult, the image of the semiconductor device 211 can be formed by moreeffectively utilizing the beam from the solid immersion lens 206.

The present embodiment adopts the configuration wherein the glass plate141 is located on the objective lens 221 side of the base part 250, butit is also possible to adopt, for example, a configuration wherein theglass plate 141 has substantially the same shape as the aperture 142 andis fitted in the aperture 142. The lens holding part 150 was describedto be detachable from and attachable to the base part 250 through themount portion 160, but it may be arranged in a state in which it isalways fixed to the base part 250. Each holding piece 262 may be burieddirectly in the glass plate 141.

The effect of the configuration wherein the lens holding part 150extends in the direction of the optical axis L is much the same as inthe case of the first embodiment, and it is thus feasible to observe theobject up to a region closer to the peripheral part 211 a of thesemiconductor device 211.

The preferred embodiments of the present invention were described above,but it is noted that the present invention is by no means limited to theabove embodiments. The configurations of the solid immersion lensholders 208A-208G according to the first to seventh embodiments can alsobe used in combination.

For example, the solid immersion lens holders 208D-208F according to thefourth to sixth embodiments may be configured so as to protect theobservation object by narrowing the width of the connecting parts inpart in each of them or by sticking the stress detection sensors ontothe respective connecting parts. Furthermore, the solid immersion lensholders 208B-208C, 208E, 208F may be configured so that the lens holdingpart is detachably attached to the base part, as the solid immersionlens holder 208D is. In a further preferred configuration, the solidimmersion lens holders 208B-208D, 208F, 208G are configured to have thediaphragm 110 as the solid immersion lens holder 208E is.

Each of the holding members 261, 291, 120, and 151 is comprised of thethree holding pieces 262, 121, but there are no particular restrictionson the number of holding pieces 262, 121 as long as the solid immersionlens 206 can be stably received. Furthermore, where each of the solidimmersion lens holders 208A-208G of the first to seventh embodiments wasapplied to the semiconductor inspection apparatus 201, the center lineof the lens holding part 260, 290, 150 was arranged to agree with theoptical axis L of the objective lens 221; however, they do not alwayshave to agree with each other. In a potential configuration, the lensholding part 260, 290, 150 extends in the direction of the optical axisL and, for example, the center line of the lens holding part 260, 290150 may be parallel to the optical axis L.

Furthermore, the first to seventh embodiments adopted the holding piecesas lens receivers, but the lens receivers are not limited to theplatelike members. The solid immersion lens holders 208A-208G of thefirst to seventh embodiments are also suitably applicable, for example,to systems for observing objects like wafers. Furthermore, the solidimmersion lens holders 208A-208G of the first to seventh embodimentswere applied to the semiconductor inspection apparatus 201, but they arealso applicable to systems for observing objects except forsemiconductors.

Further, in the above-described microscope and sample observationmethod, it is also preferable that the focusing in the normal mode, usedfor observing the normal image of the sample, is carried out by using anautomatic focusing technique for automatically controlling the focalpoint. The automatic focusing can be carried out, for example, byutilizing the contrast in the image.

For example, when the images of the sample are acquired at a pluralityof positions different from each other in the Z-axis direction, thecontrast of the image becomes larger as the focal point is matched.Accordingly, the focal point can be determined by the position with thelargest image contrast among the above plurality of positions. As forthe contrast of the image, for example, when the luminance profile ofthe image is considered as a profile surface having a three-dimensionalshape corresponding to the luminance variation in the image, thecontrast value can be evaluated by using a surface area of the profilesurface.

An example of the focusing method by using the above automatic focusingtechnique is as follows. First, an image of the sample is acquiredthrough the objective lens, and a contrast value of the obtained image(e.g. a surface area of the luminance profile) is extracted. Then, thestage carrying the sample is moved in the Z-axis direction by apredetermined distance, and again the acquisition of the image and theextraction of the contrast value are carried out. Further, the aboveoperations are repeatedly performed. Here, as for the above-describeddistance in the Z-axis direction for moving the stage carrying thesample, it is preferable that the distance is set based on theresolution and the like in the Z-axis direction.

In the above operations, if the contrast value is increased twice in arow, or the contrast value is increased once and then decreased once,the operations of moving the stage, the acquisition of the image, andthe extraction of the contrast value are repeatedly carried out. On theother hand, if the contrast value is decreased twice in a row, theposition before the decrease of the contrast value is determined as thefocal point. As for the specific focusing method, various methods can beused in addition to the above-described method.

From the invention thus described, it will be obvious that the inventionmay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedfor inclusion within the scope of the following claims.

1. A microscope for observing a sample at a predetermined observationplane, comprising: an optical system comprising an objective lens andadapted to guide an image of the sample; objective lens driving meansfor driving the objective lens to achieve focusing and aberrationcorrection for the sample; a solid immersion lens arranged at a positionincluding an optical axis from the sample to the optical system; andcontrolling means for controlling the objective lens driving means,wherein the controlling means has a solid immersion lens mode, as acontrol mode, in which the focusing and aberration correction arecarried out under a correction condition set based on a refractive indexn₀ of the sample and a thickness t₀ of the sample up to the observationplane, and a refractive index n₁, a thickness d₁, and a radius ofcurvature R₁ of the solid immersion lens.
 2. The microscope according toclaim 1, comprising solid immersion lens driving means for driving thesolid immersion lens to move the solid immersion lens between aninsertion position including an optical axis from the sample to theoptical system and a standby position off the optical axis.
 3. Themicroscope according to claim 2, wherein the optical system comprises,as the objective lens, a first objective lens for observing a normalimage of the sample, and a second objective lens for observing anenlarged image of the sample with the solid immersion lens.
 4. Themicroscope according to claim 1, wherein the controlling means comprisesa focusing table and an aberration correction table corresponding to thecorrection condition in the solid immersion lens mode.
 5. The microscopeaccording to claim 1, wherein the controlling means has two controlmodes, a normal mode in which the focusing is carried out by changing adistance between the sample and the objective lens, and the solidimmersion lens mode.
 6. The microscope according to claim 5, wherein inthe normal mode, the focusing is carried out under a normal correctioncondition set based on the refractive index n₀ of the sample and thethickness t₀ of the sample up to the observation plane.
 7. Themicroscope according to claim 6, wherein the controlling means comprisesa focusing table corresponding to the normal correction condition in thenormal mode, and a focusing table and an aberration correction tablecorresponding to the correction condition in the solid immersion lensmode.
 8. The microscope according to claim 1, wherein the objective lensdriving means comprises focusing means for changing a distance betweenthe sample and the objective lens to carry out the focusing.
 9. Themicroscope according to claim 1, wherein the objective lens comprises afirst lens unit and a second lens unit arranged along the optical axis,and wherein the objective lens driving means comprises aberrationcorrecting means for changing a spacing between the first lens unit andthe second lens unit in the objective lens to carry out the aberrationcorrection.
 10. The microscope according to claim 1, comprising a solidimmersion lens holder including a base part to be attached to theobjective lens, and a lens holding part provided with the base part,extending in a direction of the optical axis of the objective lens, andholding the solid immersion lens at an end portion thereof, wherein thelens holding part holds the solid immersion lens so that light emergingfrom the solid immersion lens to the base part side travels through aregion outside the lens holding part and toward the base part, andwherein the base part has a light passing portion which transmits thelight emerging from the solid immersion lens to the base part side,toward the objective lens.
 11. The microscope according to claim 10,wherein the lens holding part has: a holding member extending in thedirection of the optical axis and receiving the solid immersion lens;and a lens cover provided at an end portion of the holding member andhaving an opening for exposing a bottom surface of the solid immersionlens to the outside, wherein the lens holding part houses the solidimmersion lens between the holding member and the lens cover.
 12. Asample observation method of observing a sample at a predeterminedobservation plane and through an optical system comprising an objectivelens, the sample observation method comprising: a correction step ofplacing a solid immersion lens at an insertion position including anoptical axis from the sample to the optical system and carrying outfocusing and aberration correction under a correction condition setbased on a refractive index n₀ of the sample and a thickness t₀ of thesample up to the observation plane, and a refractive index n₁, athickness d₁, and a radius of curvature R₁ of the solid immersion lens;and an enlarged image observation step of observing an enlarged image ofthe sample in a state after completion of the focusing and aberrationcorrection in the correction step.
 13. The sample observation methodaccording to claim 12, wherein the correction step is arranged to use afocusing table and an aberration correction table corresponding to thecorrection condition.
 14. The sample observation method according toclaim 12, comprising a normal image observation step of observing anormal image of the sample in a state of placing the solid immersionlens at a standby position off the optical axis.
 15. The sampleobservation method according to claim 14, comprising a normal correctionstep of placing the solid immersion lens at the standby position off theoptical axis from the sample to the objective lens and carrying outfocusing by changing a distance between the sample and the objectivelens.
 16. The sample observation method according to claim 15, whereinin the normal correction step, the focusing is carried out under anormal correction condition set based on the refractive index n₀ of thesample and the thickness t₀ of the sample up to the observation plane.17. The sample observation method according to claim 16, wherein thenormal correction step is arranged to use a focusing table correspondingto the normal correction condition, and the correction step is arrangedto use a focusing table and an aberration correction table correspondingto the correction condition.
 18. The sample observation method accordingto claim 12, wherein in the correction step, the focusing is carried outby changing a distance between the sample and the objective lens. 19.The sample observation method according to claim 12, wherein in thecorrection step, the aberration correction is carried out by changing aspacing between a first lens unit and a second lens unit arranged alongthe optical axis in the objective lens.
 20. The sample observationmethod according to claim 15, wherein in the normal correction step, thefocusing is carried out by using an automatic focusing technique.